Add support for type traversal matchers.

Summary:
Fixup the type traversal macros/matchers to specify the supported types.
Make the marshallers a little more generic to support any variadic function.
Update the doc script.

Reviewers: klimek

CC: cfe-commits, revane

Differential Revision: http://llvm-reviews.chandlerc.com/D1023

llvm-svn: 186340