[RFC] Removing libclang API to generate HTML-formatted comments

Hello,

I'd like to remove the clang_FullComment_getAsHTML API from libclang.
Instead, I would recommend to use clang_FullComment_getAsXML, which
provides much more information about the comment.

Here are the reasons to remove this API:
- I don't know of any users of this API.
- The output of this API is "fixed-format", non-customizable HTML. A
single hardcoded format clearly does not fit all uses.

I think that the existing XML output is strictly superior. One can
get any desired form of HTML from it by applying an XSLT stylesheet,
for example.

Here's the plan:
Clang 3.4 -- the API is deprecated.
Clang 3.5 -- the API is removed.

Please let me know what you think.

Dmitri