Tests: Improve feature testing for skipping.

Tests: Improve feature testing for skipping.

Fixed a bug where test_compress_* would all fail if arm64 or armthumb
filters were enabled for compression but arm was disabled. Since the
grep tests only checked for "define HAVE_ENCODER_ARM", this would match
on HAVE_ENCODER_ARM64 or HAVE_ENCODER_ARMTHUMB.

Now the config.h feature test requires " 1" at the end to prevent the
prefix problem. have_feature() was also updated for this even though
there were known current bugs affecting it. This is just in case future
features have a similar prefix problem.