Simplify return for AtoI()

Just missed the boat by a minute :-)
As we're still looking at this. I was thinking, how about this:

```
    while (isSpace(*str)) str++;

    char first_char = *str;

    if (first_char == '-' || first_char == '+') str++;

    int  result = 0;
    for(; isDigit(*str); str++)
    {
        result *= 10;
        result += *str - '0';
    }
    return (first_char == '-') ? -result : result;
```
(In general, I don't like to use bool and often find that avoiding them creates nicer code)