[crossfire] Using UTF-8 in maps

[Raphaël Quinet]

Just a quick summary of what was discussed a few minutes ago on IRC, so
that it's not forgotten:
- the gtk v2 client is already using UTF-8 correctly;
- gxclient and the old gtk v1 client are still using iso-8859-1 but
  it should not be hard to convert them to UTF-8;
- UTF-8 is pretty much the standard today and it will be increasingly
  hard to justify using anything else.

Those who participated in that discussion were in favor of
standardizing on UTF-8 (at least for maps, we didn't really discuss
archetypes or anything else).  There were no objections against it.

-Raphaël