PR gdb/2474

	PR gdb/2474
	* remote.c (remote_read_description_p): New function.
	(remote_start_remote): Try to fetch the target description
	before adding shared libraries.  Try again later if the
	target is running but stopped.
	(remote_open_1): Mark extended targets as exited by default.
	(remote_read_description): Check target_has_execution.