This patch fixes several issues found when running the `make distcheck`
target:
- In commit c561b8da, the update of gstcompat.h in Makefile.am was
forgotten.
- In commit c5756a91 add the simple_encoder_source_h in EXTRA_DIST was
forgotten.
- vpx.build.stamp is not generated at all, only vpx.configure.stamp.
- The make target distcleancheck failed because some autogenerated files
were not handled with the DISTCLEANFILES variable.
Note: `make distcheck -jXX` is not currently supported.
The built-in libvpx serves multiple purposes, among which the most
important ones could be: track the most up-to-date, and optimized,
range decoder; allow for future hybrid implementations (non-VLD);
and have a completely independent range decoder implementation.
Apply correct patch from fd.o #722760 to fix several issues: update the
license terms to LGPLv2.1+, fix dependencies to built-in libvpx and fix
make dist.
Add libvpx submodule that tracks the upstream version 1.3.0. This is
needed to build a libgstcodecparsers_vpx.so library with all symbols
placed into the GSTREAMER namespace.
