Enhancements for the DynTypedMatcher system.

- Added conversion routines and checks in Matcher<T> that take a DynTypedMatcher.
- Added type information on the error messages for the marshallers.
- Allows future work on Polymorphic/overloaded matchers. We should be
  able to disambiguate at runtime and choose the appropriate overload.

llvm-svn: 184429