x86: Adapt SSSE3 mct to SSE2

└─[$] <git:(sse2)> dav1d-bench -r 3 -d -t -g HEAD~2 -m sse2 /Users/psilokos/Movies/AV1/AV1beta10.ivf
building 2b98fd286cbe6768ce9877314cba9fc4ffa11259... OK
testing 2b98fd286cbe6768ce9877314cba9fc4ffa11259... OK

running 3 time(s) (with 0 warm up runs / sleeping for 0 seconds between each run):
./tools/dav1d --cpumask=sse2 --framethreads=8 --tilethreads=4 -i /Users/psilokos/Movies/AV1/AV1beta10.ivf --muxer null -s 0 -l 0
=> 38.78333333333333333333 seconds (stdev=.21791945504908204243)

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building 70ca718d2cbcc63399f5dfd85351ce14e06588d9... OK
testing 70ca718d2cbcc63399f5dfd85351ce14e06588d9... OK

running 3 time(s) (with 0 warm up runs / sleeping for 0 seconds between each run):
./tools/dav1d --cpumask=sse2 --framethreads=8 --tilethreads=4 -i /Users/psilokos/Movies/AV1/AV1beta10.ivf --muxer null -s 0 -l 0
=> 31.23333333333333333333 seconds (stdev=.07845734863959879921)

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relative decode performance report:


- /Users/psilokos/Movies/AV1/AV1beta10.ivf:
	2b98fd286cbe6768ce9877314cba9fc4ffa11259..70ca718d2cbcc63399f5dfd85351ce14e06588d9 = 24.17289220917822838847%
    stddev_2b98fd286cbe6768ce9877314cba9fc4ffa11259=.21791945504908204243
    stddev_70ca718d2cbcc63399f5dfd85351ce14e06588d9=.07845734863959879921```