More fixes for building (test builds) x86-32/64 without MMX or SSE2.

./configure CFLAGS="-m64 -mno-sse2 -O2"
./configure CFLAGS="-m64 -mno-mmx -mno-sse -O2"

Under OSX, MMX-only works but disabling MMX seems to fail because
system libraries assume at least MMX.