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

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

Original commit message from CVS:
Patch by: Vincent Torri  <vtorri at univ-evry fr>
* configure.ac:
* sys/Makefile.am:
* sys/directsound/Makefile.am:
* sys/directsound/gstdirectsoundsink.c:
(gst_directsoundsink_reset):
Add directsoundsink to build and dist it, so it gets built when
compiling with MingW on win32 and the required headers and libraries
are available (fixes: #392638). Also simplify DirectDraw check a bit.
* tests/check/elements/.cvsignore:
Fix CVS ignore for neonhttpsrc test binary.