detect when syscall emulation isn't present

I noticed that when CONFIG_IA32_EMULATION is disabled, trinity
continually tries to 32-bit syscalls, which is pretty wasteful.
After failing N times, we now disable all 32-bit syscalls.

For now at least, n = number of pids * 2, which should give
a pretty good chance of _one_ of those succeeding if emulation
is present. We only need one success to note that we don't need
to keep checking.