Use CFLAGS_NO_SIMD where needed, and move most uses of stand-alone binaries in the system to using bsd.stand.mk.

[imp]

Summary

Use CFLAGS_NO_SIMD in preference to varying lists of -mno-xxxx flags.
Go ahead and defined -D_STANDALONE for all targets (only strictly
needed for some architecture, but harmless on those it isn't required
for). Also add -msoft-float to all architectures uniformly rather
that higgley piggley like it is today.

Move most uses of stand-alone binaries in the system to using
bsd.stand.mk.

[imp]

Justin says we don't need -DNETIF_DEBUG, so remove it for now.