Tidy up simulator testing.

2013-04-02  Jeremy Bennett <jeremy.bennett@embecosm.com>

	* arc-sim-mdb.exp: Deleted.
	* arc-sim-base.exp: Merged into arc-sim.exp
	* arc-sim.exp: Incorporate arc-sim-base.exp, add correct licensing
	header, allow multilib options to be specified by environment
	variable.