fixed bugs in windows context creation, which would result in some times

fixed bugs in windows context creation, which would result in some times
choosing non-accelerated pixel formats:
 - forgot to add the (WGL_ACCELERATION, WGL_FULL_ACCELERATION) pair to
   the attributes passed to wglChoosePixelFormat.
 - fixed attributes in the beginning of the list were overwritten by the
   addition of extra attributes due to init flags.