TemplateSpecializationType doesn't quite have getDecl(). Need to go
through TemplateName to get a TemplateDecl.
Added test cases for the hasDeclaration() overload for
TemplateSpecializationType. Also introduced the type matcher
templateSpecializationType() used by the new hasDeclaration() test case.
Updated LibASTMatchersReference.
Reviewers: klimek
llvm-svn: 176025