Replaces the C fallback (borrowed from PowerPC) with dedicated i386
assembly for all nine kernels, matching the amd64/arm64 convention.
Fixes two real bugs found and verified on physical Pentium 4 hardware:
scalar FP silently running on x87 instead of SSE2, and fm_int_math
calling __udivdi3 on every iteration of the highest-weighted test
because the C compiler didn't know its 0xdeadbeef divisor fits in 32
bits. Real-hardware SINGLECORE/MULTICORE scores go from 425/448 to
539/581.
owen