Fix multiple quality issues in the source

This PR fixes multiple issues in the source code to address issues raised by
tests/scripts/check-files.py. Specifically:
 * incorrect file permissions
 * missing newline at the end of files
 * trailing whitespace
 * Tabs present
 * TODOs in the souce code
diff --git a/library/ssl_srv.c b/library/ssl_srv.c
index aca4235..e897ff4 100644
--- a/library/ssl_srv.c
+++ b/library/ssl_srv.c
@@ -793,7 +793,7 @@
     const mbedtls_ssl_ciphersuite_t *suite_info;
 
 #if defined(MBEDTLS_SSL_PROTO_TLS1_2) && \
-    defined(MBEDTLS_KEY_EXCHANGE__WITH_CERT__ENABLED)    
+    defined(MBEDTLS_KEY_EXCHANGE__WITH_CERT__ENABLED)
     mbedtls_pk_type_t sig_type;
 #endif
 
@@ -2961,7 +2961,7 @@
             return( ret );
         }
 
-#if defined(MBEDTLS_KEY_EXCHANGE__WITH_SERVER_SIGNATURE__ENABLED)        
+#if defined(MBEDTLS_KEY_EXCHANGE__WITH_SERVER_SIGNATURE__ENABLED)
         dig_signed = p;
         dig_signed_len = len;
 #endif
@@ -3050,7 +3050,7 @@
 
         /*
          * 3.1: Choose hash algorithm:
-         * A: For TLS 1.2, obey signature-hash-algorithm extension 
+         * A: For TLS 1.2, obey signature-hash-algorithm extension
          *    to choose appropriate hash.
          * B: For SSL3, TLS1.0, TLS1.1 and ECDHE_ECDSA, use SHA1
          *    (RFC 4492, Sec. 5.4)
@@ -3071,7 +3071,7 @@
                                                           sig_alg ) ) == MBEDTLS_MD_NONE )
             {
                 MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) );
-                /* (... because we choose a cipher suite 
+                /* (... because we choose a cipher suite
                  *      only if there is a matching hash.) */
                 return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
             }