Improvements to telnet for testing.

2013-03-15  Jeremy Bennett <jeremy.bennett@embecosm.com>

	* dejagnu/telnet-extra.exp: Improve commenting throughout
	(telnet_close): Ensure we have a spawn_id for actions, unset
	spawn_id on close, declare spawn_id global.
	(telnet_exec): Clearer handling of names and args, declare
	spawn_id global.
	(telnet_spawn_open): New proc, declare spawn_id global.
	(telnet_spawn): Rewritten to use its own spawn_id, independent of
	telnet_exec, declare spawn_id global.