Bug when using uint inside loop

[Matheus]

I saw this problem in C, then I tried on GDC and have the same 
problem:

int main() {
    for (uint a = 0, b = 0; a < 6; a += 1, b += 2){
         if (b < a){
             return 1;
         }
    }
    return 0;
}

The code above generates the wrong code when using: -O1, -O2 or 
-O3:

_Dmain:
         mov     eax, 1
         ret

Changing "uint" to "int" will that, or initializing with both "a" 
and "b" with a different value like "1" instead of "0" will work 
in -01, but will keep failing for -02 or -03.

Finally initializing with negative number will work for all 3 
optimization level.

Matheus.