tools/libs: merge xenctrl_dom.h into xenguest.h

tools/libs: merge xenctrl_dom.h into xenguest.h

Today xenctrl_dom.h is part of libxenctrl as it is included by
xc_private.c. This seems not to be needed, so merge xenctrl_dom.h into
xenguest.h where its contents really should be.

Replace all #includes of xenctrl_dom.h by xenguest.h ones or drop them
if xenguest.h is already included.

Signed-off-by: Juergen Gross <jgross@suse.com>
Acked-by: Wei Liu <wl@xen.org>