gdb/

gdb/
	* NEWS: Mention qSupported.
	* remote.c (struct remote_state): Add explicit_packet_size.
	(get_remote_packet_size): Check explicit_packet_size.
	(get_memory_packet_size): Likewise.
	(PACKET_qSupported): New enum value.
	(struct protocol_feature, remote_supported_packet)
	(remote_packet_size, remote_protocol_features)
	(remote_query_supported): New.
	(remote_open_1): Reset explicit_packet_size.  Call
	remote_query_supported.
	(_initialize_remote): Register qSupported.
gdb/doc/
	* gdb.texinfo (Remote configuration): Document set / show
	remote supported-packets.
	(General Query Packets): Document qSupported packet.
gdb/gdbserver/
	* server.c (handle_query): Handle qSupported.