winex11: Don't process ConfigureNotify events that have been superseded by a later configure request.

This is functionally a revert of
8eeb513b. The language of the extension
is slightly confusing to me, but GL_STREAM_*_ARB is more dynamic than
GL_DYNAMIC_*_ARB. So use GL_STREAM usage for D3DUSAGE_DYNAMIC buffers and
GL_DYNAMIC usage for non-dynamic buffers.