Fix RC compilation, and OSD from C++ code in the process.

it did not work properly (proper check is impossible without blocking)

- Don't undef off_t twice.

Remove the sys/socket.h check. We don't really use it anyway, and socket calls have to be somewhere anyway

Reverts [24530] & [24531] (preprocessing related) , add $(DEFS) (-DHAVE_CONFIG_H) to moc command line

Qt4 - Basic implementation of the extensions. Seem to work :D Just .avi now, because we have no good list of extensions in the source code... :D
Ref #763

Qt4 - Fix Compilation on CYGWin. This is a quick fix but not a solution. Again, MOC isn't given HAVE_CONFIG_H so it can't understand ENABLE_VLM or ENABLE_UPDATE. MOCFLAGs would fix that ?

Small fix for Windows compilation... gruiking because MOC doesn't understand #ifdef WIN32... Necessary to add a MOCFLAGS in configure.ac ?

Missing some cases that I could not test.
Also ffmpeg/chroma.c is locked, so I can but leave it broken.
Fix is for the remaining modules is obvious and the issue is easy to detect.