Rule out overflowing signed divisions

Consider a signed division such as (-128::W8) / (-1::W8). GHC lowers
this to IDIV which will throw an FP exception since the 8-bit target
register is too small to accommodate the result, 128.

Therefore, we are going to specify the Quot primop as being undefined
in cases where the result overflows.

See test-primops#1.