dwarf-fortress: Update to 0.34.11.

Somehow Dwarf Fortress suddenly started failing to use our libpng (or
zlib). I tried all possible combinations (supplying them via
LD_LIBRARY_PATH in the script) but it just won't work.

This solution was found in the Archlinux bug tracker: It just symlinks
all problematic .png files to their .bmp counterparts. It's ugly and
*sadly* breaks tileset support (unless you convert them to bmp) but I
think it's acceptable, as the whole expression is pretty problematic
in terms of purity.

Let's hope the next release of Dwarf Fortress will be easier to
support.

(fixes #710)