[gdbserver] Split a new inferiors.h file out of server.h.

[gdbserver] Split a new inferiors.h file out of server.h.

gdb/gdbserver/
2013-09-05  Pedro Alves  <palves@redhat.com>

	* server.h (current_process, get_thread_process, all_processes)
	(add_inferior_to_list, for_each_inferior, current_inferior)
	(remove_inferior, add_process, remove_process, find_process_pid)
	(have_started_inferiors_p, have_attached_inferiors_p)
	(thread_id_to_gdb_id, thread_to_gdb_id, gdb_id_to_thread_id)
	(clear_inferiors, find_inferior, find_inferior_id)
	(inferior_target_data, set_inferior_target_data)
	(inferior_regcache_data, set_inferior_regcache_data): Move to
	inferiors.h, and include it.
	* inferiors.h: New file.