Update Polish translation.
Add Galician translation.
Remove wrong code from button mask loading code, bug 6065

The READ_MASK_COPY macro already uses these exact fallbacks, so these
lines just overwrote the custom bitmaps with the default fallback bitmaps.
Make theme.c indentation more locally consistent

Also removes some comments that is just the code with s/_/ /g
Reduce length of theme.c a bit