on eglCreateContext the translator created a window for the
specified config with a matching pixelformat and saved it's
device context for future use.
however when the thread exited the window was destroyed by windows
and the handle saved became invalid.
the next call to wglCreateContext with the handle saved failed.
fixed the problem by creating windows per thread and not in a
global pool.
each thread will create its own window for each config when asked
the window will be destroyed when the thread exits.
Change-Id: I63668a20e8c30c42c4cfcaca664938683600b28e
2a581c9cb2