Simple cleanup removals in remote.c

Simple cleanup removals in remote.c

This removes a few cleanups in remote.c using the usual techniques:
std::vector, unique_xmalloc_ptr, and gdb::def_vector.

ChangeLog
2017-10-16  Tom Tromey  <tom@tromey.com>

	* remote.c (remote_register_number_and_offset): Use std::vector.
	(remote_set_syscall_catchpoint): Use gdb::unique_xmalloc_ptr.
	(putpkt_binary): Use gdb::def_vector.
	(compare_sections_command): Use gdb::byte_vector.