Refactor VariantMatcher::MatcherOps to reduce the amount of generated code.

Summary:
Refactor VariantMatcher::MatcherOps to reduce the amount of generated code.
 - Make some code type agnostic and move it to the cpp file.
 - Return a DynTypedMatcher instead of storing the object in MatcherOps.

This change reduces the number of symbols generated in Registry.cpp by
~19%, the object byte size by ~17% and the compilation time (in non-release mode) by ~20%.

Reviewers: klimek

Subscribers: klimek, cfe-commits

Differential Revision: http://reviews.llvm.org/D5124