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.

mciavi: In MCI, RECT structure is used differently: rc.right = width & rc.bottom = height so do the conversion when needed.

The memory is uninitialised and so further unmarshalling shouldn't try
to reuse any memory. fMustAlloc is always set to TRUE when allocating
memory so that it is clear that the unmarshalling is safe and to avoid
future problems with change or the code being copied.