LibCrypto: Add a Hash::Manager that can act as any one of the hashes

Author: https://github.com/alimpfard
Commit: 43a49f5fff
Pull-request: https://github.com/SerenityOS/serenity/pull/1661
Reviewed-by: https://github.com/Dexesttp
Reviewed-by: https://github.com/awesomekling
Reviewed-by: https://github.com/itamar8910

Libraries/LibCrypto/Hash/MD5.h

@@ -34,7 +34,11 @@ namespace Crypto {
 namespace Hash {
 
 struct MD5Digest {
-    u8 data[16];
+    constexpr static size_t Size = 16;
+    u8 data[Size];
+
+    const u8* immutable_data() const { return data; }
+    size_t data_length() { return Size; }
 };
 
 namespace MD5Constants {