OID functionality moved to a separate module.

A new OID module has been created that contains the main OID searching
functionality based on type-dependent arrays. A base type is used to
contain the basic values (oid_descriptor_t) and that type is extended to
contain type specific information (like a pk_alg_t).

As a result the rsa sign and verify function prototypes have changed. They
now expect a md_type_t identifier instead of the removed RSA_SIG_XXX
defines.

All OID definitions have been moved to oid.h
All OID matching code is in the OID module.

The RSA PKCS#1 functions cleaned up as a result and adapted to use the
MD layer.

The SSL layer cleanup up as a result and adapted to use the MD layer.

The X509 parser cleaned up and matches OIDs in certificates with new
module and adapted to use the MD layer.

The X509 writer cleaned up and adapted to use the MD layer.

Apps and tests modified accordingly
diff --git a/library/ssl_cli.c b/library/ssl_cli.c
index 502a61a..9ad69dc 100644
--- a/library/ssl_cli.c
+++ b/library/ssl_cli.c
@@ -737,9 +737,7 @@
     size_t n;
     unsigned char *p, *end;
     unsigned char hash[64];
-    md5_context md5;
-    sha1_context sha1;
-    int hash_id = SIG_RSA_RAW;
+    md_type_t md_alg = POLARSSL_MD_NONE;
     unsigned int hashlen = 0;
 
     const ssl_ciphersuite_t *ciphersuite_info = ssl->transform_negotiate->ciphersuite_info;
@@ -834,28 +832,28 @@
         {
 #if defined(POLARSSL_MD5_C)
             case SSL_HASH_MD5:
-                hash_id = SIG_RSA_MD5;
+                md_alg = POLARSSL_MD_MD5;
                 break;
 #endif
 #if defined(POLARSSL_SHA1_C)
             case SSL_HASH_SHA1:
-                hash_id = SIG_RSA_SHA1;
+                md_alg = POLARSSL_MD_SHA1;
                 break;
 #endif
 #if defined(POLARSSL_SHA2_C)
             case SSL_HASH_SHA224:
-                hash_id = SIG_RSA_SHA224;
+                md_alg = POLARSSL_MD_SHA224;
                 break;
             case SSL_HASH_SHA256:
-                hash_id = SIG_RSA_SHA256;
+                md_alg = POLARSSL_MD_SHA256;
                 break;
 #endif
 #if defined(POLARSSL_SHA4_C)
             case SSL_HASH_SHA384:
-                hash_id = SIG_RSA_SHA384;
+                md_alg = POLARSSL_MD_SHA384;
                 break;
             case SSL_HASH_SHA512:
-                hash_id = SIG_RSA_SHA512;
+                md_alg = POLARSSL_MD_SHA512;
                 break;
 #endif
             default:
@@ -917,6 +915,9 @@
 
     if( ssl->minor_ver != SSL_MINOR_VERSION_3 )
     {
+        md5_context md5;
+        sha1_context sha1;
+
         /*
          * digitally-signed struct {
          *     opaque md5_hash[16];
@@ -942,15 +943,12 @@
         sha1_update( &sha1, ssl->in_msg + 4, n );
         sha1_finish( &sha1, hash + 16 );
 
-        hash_id = SIG_RSA_RAW;
+        md_alg = POLARSSL_MD_NONE;
         hashlen = 36;
     }
     else
     {
-        sha2_context sha2;
-#if defined(POLARSSL_SHA4_C)
-        sha4_context sha4;
-#endif
+        md_context_t ctx;
 
         n = ssl->in_hslen - ( end - p ) - 8;
 
@@ -961,66 +959,23 @@
          *     ServerDHParams params;
          * };
          */
-        switch( hash_id )
+        if( ( ret = md_init_ctx( &ctx, md_info_from_type( md_alg ) ) ) != 0 )
         {
-#if defined(POLARSSL_MD5_C)
-            case SIG_RSA_MD5:
-                md5_starts( &md5 );
-                md5_update( &md5, ssl->handshake->randbytes, 64 );
-                md5_update( &md5, ssl->in_msg + 4, n );
-                md5_finish( &md5, hash );
-                hashlen = 16;
-                break;
-#endif
-#if defined(POLARSSL_SHA1_C)
-            case SIG_RSA_SHA1:
-                sha1_starts( &sha1 );
-                sha1_update( &sha1, ssl->handshake->randbytes, 64 );
-                sha1_update( &sha1, ssl->in_msg + 4, n );
-                sha1_finish( &sha1, hash );
-                hashlen = 20;
-                break;
-#endif
-#if defined(POLARSSL_SHA2_C)
-            case SIG_RSA_SHA224:
-                sha2_starts( &sha2, 1 );
-                sha2_update( &sha2, ssl->handshake->randbytes, 64 );
-                sha2_update( &sha2, ssl->in_msg + 4, n );
-                sha2_finish( &sha2, hash );
-                hashlen = 28;
-                break;
-            case SIG_RSA_SHA256:
-                sha2_starts( &sha2, 0 );
-                sha2_update( &sha2, ssl->handshake->randbytes, 64 );
-                sha2_update( &sha2, ssl->in_msg + 4, n );
-                sha2_finish( &sha2, hash );
-                hashlen = 32;
-                break;
-#endif
-#if defined(POLARSSL_SHA4_C)
-            case SIG_RSA_SHA384:
-                sha4_starts( &sha4, 1 );
-                sha4_update( &sha4, ssl->handshake->randbytes, 64 );
-                sha4_update( &sha4, ssl->in_msg + 4, n );
-                sha4_finish( &sha4, hash );
-                hashlen = 48;
-                break;
-            case SIG_RSA_SHA512:
-                sha4_starts( &sha4, 0 );
-                sha4_update( &sha4, ssl->handshake->randbytes, 64 );
-                sha4_update( &sha4, ssl->in_msg + 4, n );
-                sha4_finish( &sha4, hash );
-                hashlen = 64;
-                break;
-#endif
+            SSL_DEBUG_RET( 1, "md_init_ctx", ret );
+            return( ret );
         }
+
+        md_starts( &ctx );
+        md_update( &ctx, ssl->handshake->randbytes, 64 );
+        md_update( &ctx, ssl->in_msg + 4, n );
+        md_finish( &ctx, hash );
     }
     
     SSL_DEBUG_BUF( 3, "parameters hash", hash, hashlen );
 
     if( ( ret = rsa_pkcs1_verify( &ssl->session_negotiate->peer_cert->rsa,
                                   RSA_PUBLIC,
-                                  hash_id, hashlen, hash, p ) ) != 0 )
+                                  md_alg, hashlen, hash, p ) ) != 0 )
     {
         SSL_DEBUG_RET( 1, "rsa_pkcs1_verify", ret );
         return( ret );
@@ -1327,8 +1282,8 @@
     int ret = 0;
     size_t n = 0, offset = 0;
     unsigned char hash[48];
-    int hash_id = SIG_RSA_RAW;
-    unsigned int hashlen = 36;
+    md_type_t md_alg = POLARSSL_MD_NONE;
+    unsigned int hashlen = 0;
 
     SSL_DEBUG_MSG( 2, ( "=> write certificate verify" ) );
 
@@ -1365,7 +1320,7 @@
          *     SHA(handshake_messages);
          */
         hashlen = 36;
-        hash_id = SIG_RSA_RAW;
+        md_alg = POLARSSL_MD_NONE;
     }
     else
     {
@@ -1387,15 +1342,13 @@
         if( ssl->transform_negotiate->ciphersuite_info->mac ==
             POLARSSL_MD_SHA384 )
         {
-            hash_id = SIG_RSA_SHA384;
-            hashlen = 48;
+            md_alg = POLARSSL_MD_SHA384;
             ssl->out_msg[4] = SSL_HASH_SHA384;
             ssl->out_msg[5] = SSL_SIG_RSA;
         }
         else
         {
-            hash_id = SIG_RSA_SHA256;
-            hashlen = 32;
+            md_alg = POLARSSL_MD_SHA256;
             ssl->out_msg[4] = SSL_HASH_SHA256;
             ssl->out_msg[5] = SSL_SIG_RSA;
         }
@@ -1412,7 +1365,7 @@
     if( ssl->rsa_key )
     {
         ret = ssl->rsa_sign( ssl->rsa_key, ssl->f_rng, ssl->p_rng,
-                             RSA_PRIVATE, hash_id,
+                             RSA_PRIVATE, md_alg,
                              hashlen, hash, ssl->out_msg + 6 + offset );
     }