Announce - Thread safety annotations no longer supported in GCC

We have decided to terminate the thread safety annotation project in
GCC.

The current implementation is in the branch google/main for those
interested in using it.  We will not be pursuing a merge into trunk.
Instead, we have started implementing the same functionality in Clang.

I've updated the wiki page and moved the branch out of the active
development branches in svn.html.


Diego.