Revert "xcb_screen: fix compilation by ignoring errors for a type of warnings"

This reverts commit c4cb6db2.

Conflicts:

	bindings/phonon
	bindings/python
	configure.ac

configure.ac

@@ -3320,7 +3320,6 @@ AS_IF([test "${enable_xcb}" != "no"], [
   PKG_CHECK_MODULES(XCB, [xcb])
   PKG_CHECK_MODULES(XCB_SHM, [xcb-shm])
   VLC_ADD_PLUGIN([screensaver xcb_x11 xcb_screen xcb_apps])
-  VLC_SET_CFLAGS_WERROR([xcb_screen], [-Wno-error=uninitialized]) # some gcc report a warning which doesn't reveal an error
 
   AS_IF([test "${enable_xvideo}" != "no"], [
     PKG_CHECK_MODULES(XCB_XV, [xcb-xv >= 1.1.90.1], [