hs_valid_platform: Fix check for SSE4.2 (#310)

hs_valid_platform: Fix check for SSE4.2 (#310)

Vectorscan requires SSE4.2 as a minimum on x86_64. For Hyperscan this
used to be SSSE3.

Applications that use the library call hs_valid_platform() to check if
the CPU fulfils this minimum requirement. However, when Vectorscan
upgraded to SSE4.2, the check was not updated. This leads to the library
trying to execute instructions that are not supported, resulting in the
application to crash.

This might not have been noticed as the CPUs that do not support SSE4.2
are rather old and unlikely to run any load where performance is an
issue. However, I believe that the library should not let the
application crash.

Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>