Fix comparisons functions

[Safety0ff]

Likely fixes fix issue #8596.
The existing code had issues with overflow and implicit narrowing conversion.

[Hackerpilot]

Looks reasonable.

[DmitryOlshansky]

LGTM

[Safety0ff]

This patch is trivial and good to go, @yebblies could you have a look at it please?

[quickfur]

LGTM.

Wow, I've only recently been realizing how often the subtraction trick doesn't work. It works in asm because of the CPU's carry bit, but that's not expressible in the high-level language, and sometimes that single bit makes all the difference between an overflow (sign bit loss between int.max - int.min and int.min - int.max) and a correct comparison. I wonder how many more places this same bug is lurking in, I've just recently fixed a couple o' them in druntime. :-(

[yebblies]

Me? ok.

[yebblies]

Auto-merge toggled on

[Safety0ff]

Thanks!