Add support for GNAT Ravenscar run-time library

Joel Brobecker
2010-09-23T18:43:17Z

I noticed that we never acted on these patches after we submitted them
back in April. This updates them, and fixes the little nits that I
mentioned to Jerome.

I am planning on committing these patches in a day or two. And I am
working on the documentation for the new commands next.