Fix type preventing Ruby.sln build on case-sensitive filesystems (Mono+Ubuntu)
http://ironruby.codeplex.com/workitem/7305

Use Stream.Null for File.open('nul').
Workaround Mono regex bug to fix `require` with IronRuby on Mono.
Merge pull request #109 from vikhyat/master

Get IronRuby `require` to work with Mono
Merge pull request #107 from ife/master

http://ironruby.codeplex.com/workitem/7305
Merge pull request #79 from head-thrash/master

Fix typo in Solutions/Ruby.sln