* remote.c: Add documentation for extended protocol operations

	* remote.c:  Add documentation for extended protocol operations
	and for thread_alive change from a couple weeks ago.
	(extended_remote_ops): Declare and define a new target vector
	for the extended remote protocol.
	(extended_remote_restart): New function to restart the remote
	server & process.
	(remote_open): Just a stub routine.
	(extended_remote_open): New function to start a remote session
	using the extended gdb remote protocol.
	(remote_open_1): New function containing code common to both
	remote_open and extended_remote_open.
	(remote_mourn, extended_remote_mourn, remote_mourn_1): Similarly.
	(extended_remote_create_inferior): New function for the extended
	remote target.
	(initialize_remote): Add the extended_remote_ops target vector.
	* gdbserver/server.c (main, case '!'): Set extended_protocol.
	(main, case 'k'): If the extended protocol is in use, kill the
	inferior then start a new one.
	(main, case 'R'): New command to restart the remote server and
	inferior process.  Only supported when using the extended
	protocol.
	(main, server loop): If the inferior terminates while using the
	extended protocol then start a new one.  If getpkt fails when
	using the extended protocol then exit.

New extended remote gdb protocol support; intended mainly for use with
the gdbserver testing framework that I'll be checking in soon.  Also
useful for interactive remote debugging since it supports "run".