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

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@186340 91177308-0d34-0410-b5e6-96231b3b80d8