Fixes hexdigest and digest specs (SHA1)

http://github.com/Jirapong/ironruby/commit/de4e34e1530b382e5e76b484d5e6ba4b2322667a
This should make digest and hexgest spec passed, however it only
support SHA1. I’m going to create more spec for other encode methods.

Files changes:
• Merlin/External.LCA_RESTRICTED/Languages/IronRuby/mspec/ironruby-
tags/library/openssl/hmac/digest_tags.txt
• Merlin/External.LCA_RESTRICTED/Languages/IronRuby/mspec/ironruby-
tags/library/openssl/hmac/hexdigest_tags.txt
• Merlin/Main/Languages/Ruby/Libraries.LCA_RESTRICTED/
Initializers.Generated.cs
• Merlin/Main/Languages/Ruby/Libraries.LCA_RESTRICTED/OpenSSL/
OpenSSL.cs

Thank you,
-Jirapong