Merge branch 'sev/xolonium' into 'master'

Xolonium font update

Since Xolonium version 2.0 (current master), I've added various pictographs and emoticons to the font,
to provide a Unicode compatible replacement of the legacy special characters.

Note:
I'm currently working on version 3.0 of Xolonium, which is a major (and hopefully final) revision.
However, it might not be ready for Xonotic 0.8. Hence I've pushed the preliminary version 2.4, which
includes up-to-date changes to the pictograph assignments.

See merge request !6