- Update KeContextToTrapFrame to support separate ContextFlags parameters in the...

- Update KeContextToTrapFrame to support separate ContextFlags parameters in the scenario where we want to convert more then the Context's flag specify
- Rename some of the internal FPU flags to external names and make them global.
- Improve context creation of new threads to initialize the virgin NPX state for new threads, to clear DR debug registers, to properly convert the context to a trap frame, to set the right segment registers, to set the debugging mark in the trap frame, and to properly set the initial eflags.
- Add stubs for upcoming support for extended/floating point registers in KeContextToTrapFrame and KeTrapFrameToContext.

svn path=/trunk/; revision=20887