Constify some commands in remote.c
    
    gdb/ChangeLog
    2017-09-27  Tom Tromey  <tom@tromey.com>
    
    	* remote.c (set_memory_packet_size)
    	(set_memory_write_packet_size, show_memory_write_packet_size)
    	(set_memory_read_packet_size, show_memory_read_packet_size)
    	(compare_sections_command, packet_command, remote_put_command)
    	(remote_get_command, remote_delete_command): Constify.