[patch][wwwdocs] Add page describing DWARF thread-safety annotations

[Cary Coutant <ccoutant at google dot com>]

The wiki page for the thread-annotations branch of gcc --

  http://gcc.gnu.org/wiki/ThreadSafetyAnnotation

currently points to a paper in Google Docs, written by Jaeheon Yi,
that describes the DWARF extensions for recording the thread-safety
annotations.

I've been asked to move that paper to gnu.org, so that we can
reference it from comments in include/dwarf2.h. The attached patch
puts an HTML version of that paper in
projects/thread-annotations.html.

After this is committed, I'll modify the wiki project page to refer to
the new page for the DWARF details.

Is this OK to commit?

-cary

Attachment: www-thread-safety.patch.txt
Description: Text document