Merge branch 't/ipc'

Merge branch 't/ipc'

	4d9f41 mutex_get(): Change parameter from key_t to int.
	55c90e Implement --reload.
	492928 Add the --kill subcommand.
	dd42f7 Use semaphore locking to avoid starting dss multiple times.
	17eea8 Introduce get_config_file_name().

That topic was cooking in next for a quite some time now.