gstreamer1.0-omx: Transition to meson based build

gstreamer1.0-omx: Transition to meson based build

* Removed autotools/M4 specific bits from recipe.

* gettext, gtk-doc, and valgrind support is no longer present in gst-omx,
  and arguably never really was (because they were present in the "common"
  git submodule that is no longer being used in meson base builds).

Signed-off-by: Carlos Rafael Giani <crg7475@mailbox.org>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>