Log Message:
libva: clean up va_trace.c patch, hard-code gallium, appease libtool.

have an else case for the va_trace.c else patch, it seems to work
fine. not sure if the thread id needs to exist for anything, but
provide it anyway.

if we don't hard-code galilum, in the case of nouveau, it'll attempt
to use nouveau - which doesn't define __vaDriverInit_0_39. only gallium
does, so force it.
this way it works without specifying env LIBVA_DRIVER_NAME.

don't use -ldl in the makefile, it makes libtool angry (restoring
old patch-ad), although I haven't checked whether it works without
the patch.

the available.mk file is probably bogus, and I'd really like to only
rule out platforms if a problem shows up (rather than assume one exists),
but I won't change the world order.

tested with mpv --vo=vaapi (after adding libva as a dependency),
nvidia GTX 770 (nouveau) on NetBSD. it claims to be using vaapi and
plays a video fine.

bump PKGREVISION.