WIP: gnu: Add braid.
- nonfree/packages/braid.scm (braid): New variable.
It does not work yet. Launcher works but game does not start with
env LD_LIBRARY_PATH=/gnu/store/3b1drsbns6addrpb988mhlsm2bzvbwb0-braid-2015-06-11/share/braid/ /gnu/store/3b1drsbns6addrpb988mhlsm2bzvbwb0-braid-2015-06-11/share/braid/Braid.bin.x86