Jtuc convinced me we really don't need dynamic tempfile
names. So this patch changes tempfile names to be
hardcoded. And now we ask temp path in
One thing I'm not sure is if we should delete temp
files at end of CMergeDoc::Rescan(). It would ensure we
are not leaving them. But we don't need to delete those
files, we are overwriting them at next Rescan().
This patch also fixes one inefficiency with temp files.
First Rescan() called InitTempFiles() which used
CopyFile() to copy userfiles to temp path. But right
after InitTempFiles() we were calling SaveToFile() to
save buffers to temp files...