The signal.h header doesn't need to include object.h. Replace it with a
forward declaration, and instead include object.h in source files that
require it. It can speed up compilation a little bit, but more
importantly avoids unintended dependencies from the Signal class to the
Object class to be added later as the compiler will catch them.
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Milan Zamazal <mzamazal@redhat.com>
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