Pointer comparators and difference match the C standard.

Fixed two issues with pointer operations.
C11 6.5.6.9: Ptr subtraction have type ptrdiff_t.
C11 6.5.8.6, 6.5.9.3: Ptr comparisons have type int.
FYI "long long" and long are both 64 bit on 64 bit Unix, so whichever we define ptrdiff_t as a synonym for "long long" or long, it wouldn't make any observable difference. I double check the rule of the usual arithmetic conversion. They should yield the same result.

long is better than "long long" because it's used commonly more than long long.