Remove DynCastMatcher, since it is pretty much the same as Matcher<T>::WrappedMatcher.

Summary:
Remove DynCastMatcher, since it is pretty much the same as Matcher<T>::WrappedMatcher.
This reduces the number of template instantiations and number of symbols in the object file.

Reviewers: klimek

CC: cfe-commits, revane

Differential Revision: http://llvm-reviews.chandlerc.com/D1560

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@189800 91177308-0d34-0410-b5e6-96231b3b80d8