If the file ".dfhackrc" exists in the user's home directory or in the
game directory it will be sourced, so the user can set environmental
variables like LD_LIBRARY_PATH. There's also a few shell variables it
can set to alter the behavior of the dfhack script.
1) Giving "-g" or "--gdb" as the first argument to the dfhack script
will launch DF under gdb.
2) "reset -I" is called after DF finishes, to return the terminal to a
sane state in case DF crashed or was killed.
Copy package/linux/dfhack to the games directory; it's the same as the
normal df script, but sets LD_PRELOAD properly.
Also, CMAkeLists.txt now checks to see that the output directory is set
to the game directory, and fatally fails if it isn't.