This fixes 36-compare-arithmetic.c
* module/mescc/i386/as.scm (i386:r0/r1, i386:r0%r1): Do not reset
signed?.
* module/mescc/x86_64/as.scm (x86_64:r0/r1, x86_64:r0%r1): Likewise.
* lib/tests/scaffold/36-compare-arithmetic.c (main): Use unique exit
value per failure.