* stage0/x86.M1 (ja32, jae32, jb32, jbe32): New macro.
* module/mes/as-i386.mes (i386:jump-a, i386:jump-ae, i386:jump-b,
i386:jump-be): Use it in new function.
* module/mes/as-i386.scm: Export them.
* module/language/c99/compiler.mes (test-jump-label->info): Use them to
support unsigned comparison.
* scaffold/tests/7s-unsigned-compare.c: Test it.
* build-aux/check-mescc.sh (tests): Run it.
