textgen: Reduce height of lowercase graphics.

If a text string contains all lower-case characters, then generate
it at a reduced height. This is necessary for certain graphics, like
the WIF graphic ("FINISHED") on the intermission screen, otherwise
it ends up in the wrong location (#49).

Adjust the offsets for some graphics in the build config to
compensate, and fix up the vertical offsets for WICOLON/WIMINUS while
we're at it.
graphics: Depluralize victims/killers graphics.

The "victims" graphic was slightly too wide, so that it was getting
overwritten by the green square to its right on the deathmatch
intermission screen. Truncate to "victim" (and "killer") so that
it fits. This fixes #49.

Also adjust the brightness/contrast on these images to match the
other text.