Fixes for SSE detection and propagation
Fixes for SSE detection and propagation

On a machine without SSE4.1 the HAVE_SSE flag would still be set.
Because CFLAGS is set to include -msse4.2, the compiler happily
generates SSE 4.2 instructions. Running any resulting SSE-enabled
binary would then result in an illegal instruction error.

The HAVE_SSE check now checks for the presence of one of the SSE 4.1
instructions that is used in the SSE enabled convolutional decoder.
The check must run with -march=native to ensure it checks against the
host machine capabilities.

The HAVE_SSE definition is now propagated to downstream targets that
depend on libcorrect. This means they can now ifdef on HAVE_SSE to
decide whether or not to include libcorrect's SSE specific header.

Confirmed that the HAVE_SSE check now fails on an old machine without
SSE 4.1 (but with SSE 3 and SSSE 3).

quiet/libcorrect,quiet/libcorrect