Add bug tracker URL to Cabal file.

Ignore-this: dd88daf4f606a4d338689c7e2e30789

darcs-hash:20140609215935-4d2ae-e0e78be772678bfaf02186676d250723eb9fbb2f
Display runtime warning when using the non-threaded RTS.

Ignore-this: 530ff044cf339d0cae530dfd4561b929

darcs-hash:20140609223530-4d2ae-90b669c2fd0795871a08dd74452b430cd52dae0c