Doing the levels calculation before the object is created prevents leaking
resources and avoids changing baseTexture.levels after it's been initialized
by basetexture_init().

Windowless richedit control will not be able to call GetCapture without
a handle to the host window (and there is no ITextHost_TxGetCapture
method), but there is a ITextHost_TxSetCapture method available for
setting and releasing the capture on the mouse.  This means that the
richedit control will need to keep track of whether it has captured the
mouse or not to implement windowless richedit controls.

Previously the WM_NCCREATE was handled by the as if it was always for
later versions, then the window proc for version 1.0 would make
appropriate changes afterwards.  Instead both versions should call the
same function (e.g. ME_MakeEditor) and provide the value for
bEmulateVersion10 to make the code clearer.