At the same time, the change to the player loop prevents a buffer
overshoot and a (perhaps unlikely) program trace where a sequence
Suspend; Stop; midiStreamOut could send MOM_DONE twice and access
memory possibly released within a MOM_DONE DCB_FUNCTION callback.

Found by Valgrind.

Found by Valgrind.

Fixes a regression caused by 1ff99231.

For print preview it will take more time to wait for the whole text to be
wrapped for EM_FORMATRANGE than to wait for just the first page.  Trying to
get the total number of pages will cause the whole test to be wrapped.
Instead all that is needed is to just determine if a page is the last page,
which can be determined by it's page end offset compared to the text length.

This avoids having to delete the device context and the bitmap selected
into it just to update the bitmap, since it was setting preview.hdc to
NULL to indicate that these bitmaps needed to be updated. This patch
also helps make WM_PAINT messages get processed faster by moving this out
of the code for handling WM_PAINT.

Previously hdc2 needed to be deleted and set to NULL to indicate that only
one page should be shown. I have avoided this using a new variable for
the preview structure.

The device context were also being deleted without deleting the bitmaps
created for them and selected into them, so this patch also gets these
bitmaps and deletes them with their device context.