Add libclang APIs to walk comments ASTs and an API to convert a comment to an
HTML fragment.

For testing, c-index-test now has even more output:
* HTML rendering of a comment
* comment AST tree dump in S-expressions like Comment::dump(), but implemented
* with libclang APIs.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@160577 91177308-0d34-0410-b5e6-96231b3b80d8
10 files changed