Stack overflow on 64-bit modulus operations on 32-bit architectures.

Stack overflow on 64-bit modulus operations on 32-bit architectures.

Running 'zpool create' on a 32-bit machine with an SPL compiled with
gcc 4.4.4 led to a stack overlow.  This turned out to be due to some
sort of 'optimization' by gcc:

uint64_t __umoddi3(uint64_t dividend, uint64_t divisor)
{
   return dividend - divisor * (dividend / divisor);
}

This code was supposed to be using __udivdi3 to implement /, but gcc
instead implemented it via __umoddi3 itself.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>