[MP] Use XDG_DATA_HOME env for unix (non-mac) by default.
$(XDG_DATA_HOME)/openjk.
New fall-back location: ~/.local/share/openjk
~/.openjk no longer used or checked.
[SP] Use XDG_DATA_HOME env for unix (non-mac) by default.
$(XDG_DATA_HOME)/openjk.
New fall-back location: ~/.local/share/openjk
~/.openjk no longer used or checked.