Begin sketching out the Clang release notes. The plan is to link to

Begin sketching out the Clang release notes. The plan is to link to
these more detailed notes from the primary LLVM release notes for Clang.
This gives us a nice place to flesh out in plenty of detail the major
changes that have happened in Clang land since 2.9.

I've outlined a very rough structure based on the LLVM release notes
structure and what seems like useful divisions in the Clang landscape
(e.g., language-specific stuff is relevant to a narrower audience).

I'll be first converting my brain-dump-ish notes from the commit logs,
and then cleaning here. Suggestions on structure welcome. Typo
corrections, spelling fixes (oh how I'll need them), all welcome; just
commit away.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@145233 91177308-0d34-0410-b5e6-96231b3b80d8