Introduce, and implement as usefully as I can in all front ends, a

Introduce, and implement as usefully as I can in all front ends, a
new function in the drawing API which permits the display of text
from outside basic ASCII. A fallback mechanism is provided so that
puzzles can give a list of strings they'd like to display in order
of preference and the system will return the best one it can manage;
puzzles are required to cope with ASCII-only front ends.

git-svn-id: svn://svn.tartarus.org/sgt/puzzles@8793 cda61777-01e9-0310-a592-d414129be87e