Log Message:
libva: fix build with netbsd base X11.

netbsd base X11 will have MesaLib already, which we can't do for pkgsrc
Xorg as it introduces a circular dependency. disable building the dummy
driver (which isn't really useful anyway).

disable some glx stuff that is auto-detected in the base Xorg case, again
to avoid a PLIST mismatch.

bump PKGREVISION