Add directdrawsink to build and dist it, so it gets built when compiling with MingW...

Add directdrawsink to build and dist it, so it gets built when compiling with MingW on win32 and the required headers...

Original commit message from CVS:
Patch by: Vincent Torri  <vtorri at univ-evry fr>
* configure.ac:
* sys/Makefile.am:
* sys/directdraw/Makefile.am:
Add directdrawsink to build and dist it, so it gets built when
compiling with MingW on win32 and the required headers and libraries
are available (fixes: #392313).
* sys/directdraw/gstdirectdrawsink.c:
(gst_directdrawsink_center_rect), (gst_directdrawsink_show_frame),
(gst_directdrawsink_setup_ddraw),
(gst_directdrawsink_surface_create):
Comment out some unused things and fix some printf format issues in
order to avoid warnings when buildling with MingW (#392313).