[commit v2] ravenscar-thread support updates

[Joel Brobecker]

Hello,

Re: http://www.sourceware.org/ml/gdb-patches/2012-12/msg00500.html
This patch series show the changes that I ended up checking in.

The last patch is something I noticed at the very last second,
but unfortunately after the patch went in CVS; it's git that
told me about a trailing space which highlighted the one omission.

Tested on x86_64-linux. It's hard for me to maintain two copies
of this code, so I went ahead, and checked everything in, based
on the feedback received so far.