Missing API Type::getAsTypedefType

We have APIs like getAsBuiltintype(), getAsFunctionType() in the Type
class defined in AST/Type.h.
Should we also have getAsTypedefType() in there?
I need it for handling typedefs during debug info generation.

- Sanjiv

Done: http://lists.cs.uiuc.edu/pipermail/cfe-commits/Week-of-Mon-20080512/005675.html

Cool.

-Sanjiv