gdb/server/

	gdb/server/
	* server.c (gdb_read_memory): Change return semantics to allow
	partial transfers.
	(handle_search_memory_1): Adjust.
	(process_serial_event) <'m' packet>: Handle partial transfers.
	* tracepoint.c (traceframe_read_mem): Handle partial transfers.

	gdb/testsuite/
	* gdb.trace/collection.c (global_pieces): New.
	* gdb.trace/collection.exp (gdb_collect_global_in_pieces_test):
	New procedure.
	(gdb_trace_collection_test): Call it.