The next batch of updates towards D2 support. The lib should be pretty close to...

The next batch of updates towards D2 support.  The lib should be pretty close to compiling with D2 now, and the D2 runtime changes have been reduced to a compact set of pure additions (few/no alterations).  Next update will be aimed at finishing the process of getting the lib to build with -w set under D2, which will mean adding "override" where necessary to the compiler runtime as well as figuring out how to deal with the use of 'volatile' in the thread code.

git-svn-id: http://svn.dsource.org/projects/druntime/trunk@6 4a9d5153-6564-4b3f-b5e1-7e8e9dac548f