minetest: LuaJIT, in-app mod store, better fonts and enable translations

cURL was already a dependency, but the build was having some trouble
finding the headers. Just give it a little help and the in-app mod store
store actually works.

The rest of the configuration brings us closer to other distros, like
Fedora (LuaJIT)[1] and Debian (LuaJIT, LevelDB, FreeType, gettext)[2][3]

[1] http://pkgs.fedoraproject.org/cgit/minetest.git/tree/minetest.spec#n28
[2] https://anonscm.debian.org/cgit/pkg-games/minetest-v04x.git/tree/debian/control#n9
[3] https://anonscm.debian.org/cgit/pkg-games/minetest-v04x.git/tree/debian/rules#n56