Revert "Refactor DynTypedMatcher into a value type class, just like Matcher<T>."

This reverts commit r193100.

It was failing to compile with MSVC 2012 while instantiating
llvm::Optional<DynTypedMatcher>.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@193123 91177308-0d34-0410-b5e6-96231b3b80d8