Add target_ops argument to to_supports_multi_process

Add target_ops argument to to_supports_multi_process

2014-02-19  Tom Tromey  <tromey@redhat.com>

	* target.h (struct target_ops) <to_supports_multi_process>: Add
	argument.
	(target_supports_multi_process): Add argument.
	* target.c (update_current_target): Update.
	* remote.c (remote_supports_multi_process): Add 'self' argument.
	* linux-nat.c (linux_nat_supports_multi_process): Add 'self'
	argument.
	* darwin-nat.c (darwin_supports_multi_process): Add 'self'
	argument.