Allies don't have lighter colour tint

[tmewett]

Reported by blossom. Screenshot from 1.8.2:

Screenshot from 1.8.3:

[tmewett]

The issue is this section of getCellAppearance in IO.c:

if (monst->creatureState == MONSTER_ALLY
    && (monst->info.displayChar >= 'a' && monst->info.displayChar <= 'z' || monst->info.displayChar >= 'A' && monst->info.displayChar <= 'Z')) {
    if (rogue.trueColorMode) {
        cellForeColor = white;
    } else {
        applyColorAverage(&cellForeColor, &pink, 50);
    }
}

The test for an alphabetical displayChar is so that summoned "ally-only" creatures such as guardian spirits and spectral blades aren't pink. We need an alternative to this test as displayChars are now a more generic enum type