[libclang 3/8] Add support for AttributedType

[libclang 3/8] Add support for AttributedType

Summary:
This patch adds support to the libclang API for identifying AttributedTypes in CXTypes and reading the modified type that the type points to. Currently AttributedTypes are skipped. This patch continues to skip AttributedTypes by default, but adds a parsing option to CXTranslationUnit to include AttributedTypes.

This patch depends on D49066 since it also adds a CXType.

Testing will be added in another patch which depends on this one.

Reviewers: yvvan, jbcoe

Reviewed By: yvvan

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D49081

llvm-svn: 338808