Add a missing newline at EOF

This was mentioned in issue #44.

src/md5.h

@@ -42,4 +42,4 @@ extern void MD5_Init(MD5_CTX *ctx);
 extern void MD5_Update(MD5_CTX *ctx, const void *data, unsigned long size);
 extern void MD5_Final(unsigned char *result, MD5_CTX *ctx);
 
-#endif
+#endif