Teach TreeTransform and family how to transform generic lambdas within templates and nested within themselves.

This does not yet include capturing (that is next).

Please see test file for examples.

This patch was LGTM'd by Doug:
http://llvm-reviews.chandlerc.com/D1784
http://lists.cs.uiuc.edu/pipermail/cfe-commits/Week-of-Mon-20130930/090048.html

When I first committed this patch - a bunch of buildbots were unable to compile the code that VS2010 seemed to compile.  Seems like there was a dependency on Sema/Template.h which VS did not seem to need, but I have now added for the other compilers.  It still compiles on Visual Studio 2010 - lets hope the buildbots remain quiet (please!)
Replace C++ style comment with a C style comment to satisfy some of the build bots.