gdb/

gdb/
	* NEWS: Document the new gdbserver --once option.

gdb/doc/
	* gdb.texinfo (Starting and Stopping Trace Experiments): New anchor
	for disconnected tracing.
	(Multi-Process Mode for @code{gdbserver}): Mention --multi and
	extended-remote relationship.  Mention --once.
	(TCP port allocation lifecycle of @code{gdbserver}): New.

gdb/gdbserver/
	* remote-utils.c (handle_accept_event): Close LISTEN_DESC only if
	RUN_ONCE.  Comment for the LISTEN_DESC delete_file_handler call.
	(remote_prepare): New function with most of the TCP code from ...
	(remote_open): ... here.  Detect PORT here unconditionally.  Move also
	setting transport_is_reliable.
	* server.c (run_once): New variable.
	(gdbserver_usage): Document it.
	(main): Set run_once for `--once'.  Call remote_prepare.  Exit after
	the first run if RUN_ONCE.
	* server.h (run_once, remote_prepare): New declarations.

gdb/testsuite/
	* gdb.base/solib-disc.exp: Set gdbserver_reconnect_p.
	* lib/gdb.exp (gdb_init): Clear gdbserver_reconnect_p.
	* lib/gdbserver-support.exp (gdbserver_start): Add `--once' if
	!gdbserver_reconnect_p..
	(gdbserver_reconnect): Call error if !gdbserver_reconnect_p..