Frotz

This patch adds partial mouse support to the ncurses version of Frotz. It
doesn't keep track of which mouse buttons are pressed (I wasn't able to get
that to work), but it should handle normal clicks well enough to use the
menus in Journey, for instance.

It checks for USE_NCURSES_H, so it's disabled by the default Makefile. This
could be avoided by only checking NCURSES_MOUSE_VERSION, I guess.