gdb/

	gdb/
	* target.c (target_read_live_memory): New function.
	(memory_xfer_live_readonly_partial): New.
	(memory_xfer_partial): If reading from a traceframe, fallback to
	reading unavailable read-only memory from read-only regions of
	live target memory.
	* tracepoint.c (disconnect_tracing): Adjust.
	(set_current_traceframe): New, factored out from
	set_traceframe_number.
	(set_traceframe_number): Reimplement to only change the traceframe
	number on the GDB side.
	(do_restore_current_traceframe_cleanup): Adjust.
	(make_cleanup_restore_traceframe_number): New.
	(cur_traceframe_number): New global.
	(tfile_open): Set cur_traceframe_number to no traceframe.
	(set_tfile_traceframe): New function.
	(tfile_trace_find): If looking up a traceframe using any method
	other than by number, make sure the current tfile traceframe
	matches gdb's current traceframe.  Update the current tfile
	traceframe if the lookup succeeded.
	(tfile_fetch_registers, tfile_xfer_partial)
	(tfile_get_trace_state_variable_value): Make sure the remote
	traceframe matches gdb's current traceframe.
	* remote.c (remote_traceframe_number): New global.
	(remote_open_1): Set it to -1.
	(set_remote_traceframe): New function.
	(remote_fetch_registers, remote_store_registers)
	(remote_xfer_memory, remote_xfer_partial)
	(remote_get_trace_state_variable_value): Make sure the remote
	traceframe matches gdb's current traceframe.
	(remote_trace_find): If looking up a traceframe using any method
	other than by number, make sure the current remote traceframe
	matches gdb's current traceframe.  Update the current remote
	traceframe if the lookup succeeded.
	* infrun.c (fetch_inferior_event): Adjust.
	* tracepoint.h (set_current_traceframe): Declare.
	(get_traceframe_number, set_traceframe_number): Add describing
	comments.