Also remove now unused AVFormatParameters struct and
AVOutputFormat.set_parameters().

The lavf-ffm test results change because ffmenc writes
AVCodecContext.flags/flags2 and the defaults for those change.

E.g. non_linear_quant mpeg2video private option.
Signed-off-by: Anton Khirnov <anton@khirnov.net>

Assemblers don't understand ! in %if statements.

Also implement sse2/ssse3/avx versions.

This allows combining multiple conditionals in a single statement.