SHA2 renamed to SHA256, SHA4 renamed to SHA512 and functions accordingly

The SHA4 name was not clear with regards to the new SHA-3 standard. So
SHA2 and SHA4 have been renamed to better represent what they are:
SHA256 and SHA512 modules.
diff --git a/include/polarssl/sha4.h b/include/polarssl/sha4.h
index 450ef59..711353a 100644
--- a/include/polarssl/sha4.h
+++ b/include/polarssl/sha4.h
@@ -39,9 +39,9 @@
   #define UL64(x) x##ULL
 #endif
 
-#define POLARSSL_ERR_SHA4_FILE_IO_ERROR                -0x007A  /**< Read/write error in file. */
+#define POLARSSL_ERR_SHA512_FILE_IO_ERROR              -0x007A  /**< Read/write error in file. */
 
-#if !defined(POLARSSL_SHA1_ALT)
+#if !defined(POLARSSL_SHA512_ALT)
 // Regular implementation
 //
 
@@ -62,7 +62,7 @@
     unsigned char opad[128];    /*!< HMAC: outer padding        */
     int is384;                  /*!< 0 => SHA-512, else SHA-384 */
 }
-sha4_context;
+sha512_context;
 
 /**
  * \brief          SHA-512 context setup
@@ -70,7 +70,7 @@
  * \param ctx      context to be initialized
  * \param is384    0 = use SHA512, 1 = use SHA384
  */
-void sha4_starts( sha4_context *ctx, int is384 );
+void sha512_starts( sha512_context *ctx, int is384 );
 
 /**
  * \brief          SHA-512 process buffer
@@ -79,7 +79,7 @@
  * \param input    buffer holding the  data
  * \param ilen     length of the input data
  */
-void sha4_update( sha4_context *ctx, const unsigned char *input, size_t ilen );
+void sha512_update( sha512_context *ctx, const unsigned char *input, size_t ilen );
 
 /**
  * \brief          SHA-512 final digest
@@ -87,15 +87,15 @@
  * \param ctx      SHA-512 context
  * \param output   SHA-384/512 checksum result
  */
-void sha4_finish( sha4_context *ctx, unsigned char output[64] );
+void sha512_finish( sha512_context *ctx, unsigned char output[64] );
 
 #ifdef __cplusplus
 }
 #endif
 
-#else  /* POLARSSL_SHA4_ALT */
+#else  /* POLARSSL_SHA512_ALT */
 #include "sha4_alt.h"
-#endif /* POLARSSL_SHA4_ALT */
+#endif /* POLARSSL_SHA512_ALT */
 
 #ifdef __cplusplus
 extern "C" {
@@ -109,8 +109,8 @@
  * \param output   SHA-384/512 checksum result
  * \param is384    0 = use SHA512, 1 = use SHA384
  */
-void sha4( const unsigned char *input, size_t ilen,
-           unsigned char output[64], int is384 );
+void sha512( const unsigned char *input, size_t ilen,
+             unsigned char output[64], int is384 );
 
 /**
  * \brief          Output = SHA-512( file contents )
@@ -119,9 +119,9 @@
  * \param output   SHA-384/512 checksum result
  * \param is384    0 = use SHA512, 1 = use SHA384
  *
- * \return         0 if successful, or POLARSSL_ERR_SHA4_FILE_IO_ERROR
+ * \return         0 if successful, or POLARSSL_ERR_SHA512_FILE_IO_ERROR
  */
-int sha4_file( const char *path, unsigned char output[64], int is384 );
+int sha512_file( const char *path, unsigned char output[64], int is384 );
 
 /**
  * \brief          SHA-512 HMAC context setup
@@ -131,8 +131,8 @@
  * \param key      HMAC secret key
  * \param keylen   length of the HMAC key
  */
-void sha4_hmac_starts( sha4_context *ctx, const unsigned char *key, size_t keylen,
-                       int is384 );
+void sha512_hmac_starts( sha512_context *ctx, const unsigned char *key,
+                         size_t keylen, int is384 );
 
 /**
  * \brief          SHA-512 HMAC process buffer
@@ -141,7 +141,7 @@
  * \param input    buffer holding the  data
  * \param ilen     length of the input data
  */
-void sha4_hmac_update( sha4_context *ctx, const unsigned char *input, size_t ilen );
+void sha512_hmac_update( sha512_context *ctx, const unsigned char *input, size_t ilen );
 
 /**
  * \brief          SHA-512 HMAC final digest
@@ -149,14 +149,14 @@
  * \param ctx      HMAC context
  * \param output   SHA-384/512 HMAC checksum result
  */
-void sha4_hmac_finish( sha4_context *ctx, unsigned char output[64] );
+void sha512_hmac_finish( sha512_context *ctx, unsigned char output[64] );
 
 /**
  * \brief          SHA-512 HMAC context reset
  *
  * \param ctx      HMAC context to be reset
  */
-void sha4_hmac_reset( sha4_context *ctx );
+void sha512_hmac_reset( sha512_context *ctx );
 
 /**
  * \brief          Output = HMAC-SHA-512( hmac key, input buffer )
@@ -168,7 +168,7 @@
  * \param output   HMAC-SHA-384/512 result
  * \param is384    0 = use SHA512, 1 = use SHA384
  */
-void sha4_hmac( const unsigned char *key, size_t keylen,
+void sha512_hmac( const unsigned char *key, size_t keylen,
                 const unsigned char *input, size_t ilen,
                 unsigned char output[64], int is384 );
 
@@ -177,10 +177,10 @@
  *
  * \return         0 if successful, or 1 if the test failed
  */
-int sha4_self_test( int verbose );
+int sha512_self_test( int verbose );
 
 /* Internal use */
-void sha4_process( sha4_context *ctx, const unsigned char data[128] );
+void sha512_process( sha512_context *ctx, const unsigned char data[128] );
 
 #ifdef __cplusplus
 }