New MD API: rename functions from _ext to _ret

The _ext suffix suggests "new arguments", but the new functions have
the same arguments. Use _ret instead, to convey that the difference is
that the new functions return a value.
diff --git a/include/mbedtls/md4.h b/include/mbedtls/md4.h
index f5d335d..acd09bd 100644
--- a/include/mbedtls/md4.h
+++ b/include/mbedtls/md4.h
@@ -86,7 +86,7 @@
  *
  * \return         0 if successful
  */
-int mbedtls_md4_starts_ext( mbedtls_md4_context *ctx );
+int mbedtls_md4_starts_ret( mbedtls_md4_context *ctx );
 
 /**
  * \brief          MD4 process buffer
@@ -97,7 +97,7 @@
  *
  * \return         0 if successful
  */
-int mbedtls_md4_update_ext( mbedtls_md4_context *ctx,
+int mbedtls_md4_update_ret( mbedtls_md4_context *ctx,
                             const unsigned char *input,
                             size_t ilen );
 
@@ -109,7 +109,7 @@
  *
  * \return         0 if successful
  */
-int mbedtls_md4_finish_ext( mbedtls_md4_context *ctx,
+int mbedtls_md4_finish_ret( mbedtls_md4_context *ctx,
                             unsigned char output[16] );
 
 /**
@@ -132,20 +132,20 @@
 /**
  * \brief          MD4 context setup
  *
- * \deprecated     Superseded by mbedtls_md4_starts_ext() in 2.5.0
+ * \deprecated     Superseded by mbedtls_md4_starts_ret() in 2.5.0
  *
  * \param ctx      context to be initialized
  */
 MBEDTLS_DEPRECATED static inline void mbedtls_md4_starts(
                                                     mbedtls_md4_context *ctx )
 {
-    mbedtls_md4_starts_ext( ctx );
+    mbedtls_md4_starts_ret( ctx );
 }
 
 /**
  * \brief          MD4 process buffer
  *
- * \deprecated     Superseded by mbedtls_md4_update_ext() in 2.5.0
+ * \deprecated     Superseded by mbedtls_md4_update_ret() in 2.5.0
  *
  * \param ctx      MD4 context
  * \param input    buffer holding the data
@@ -156,13 +156,13 @@
                                                     const unsigned char *input,
                                                     size_t ilen )
 {
-    mbedtls_md4_update_ext( ctx, input, ilen );
+    mbedtls_md4_update_ret( ctx, input, ilen );
 }
 
 /**
  * \brief          MD4 final digest
  *
- * \deprecated     Superseded by mbedtls_md4_finish_ext() in 2.5.0
+ * \deprecated     Superseded by mbedtls_md4_finish_ret() in 2.5.0
  *
  * \param ctx      MD4 context
  * \param output   MD4 checksum result
@@ -171,7 +171,7 @@
                                                     mbedtls_md4_context *ctx,
                                                     unsigned char output[16] )
 {
-    mbedtls_md4_finish_ext( ctx, output );
+    mbedtls_md4_finish_ret( ctx, output );
 }
 
 /**
@@ -213,7 +213,7 @@
  *
  * \return         0 if successful
  */
-int mbedtls_md4_ext( const unsigned char *input,
+int mbedtls_md4_ret( const unsigned char *input,
                      size_t ilen,
                      unsigned char output[16] );
 
@@ -226,7 +226,7 @@
 /**
  * \brief          Output = MD4( input buffer )
  *
- * \deprecated     Superseded by mbedtls_md4_ext() in 2.5.0
+ * \deprecated     Superseded by mbedtls_md4_ret() in 2.5.0
  *
  * \param input    buffer holding the data
  * \param ilen     length of the input data
@@ -236,7 +236,7 @@
                                                    size_t ilen,
                                                    unsigned char output[16] )
 {
-    mbedtls_md4_ext( input, ilen, output );
+    mbedtls_md4_ret( input, ilen, output );
 }
 
 #undef MBEDTLS_DEPRECATED