Remove the '-plain' command-line option.

It was the same as adding 'char_set = ascii' to your rcfile (we always
encode in UTF-8 no matter what).
Don't base behavior on beam names.

...with exceptions still existing for one of the Upheaval effects,
and several draconian breaths. Not sure how to resolve them without
adding even more SPELL_ enums.
Make ghosts not a ' ' (#9132).

As tempting as it is to ape NetHack...
Don't give draconian player illusions two breath attacks.