* bus/bus.c (process_config_every_time): Drop existing conf-dir
watches (if applicable) and add new watches
* bus/main.c (signal_handler): Handle SIGIO if using D_NOTIFY
(main): Setup SIGIO signal handler if using D_NOTIFY
* bus/config-parser.h: Add prototype bus_config_parser_get_conf_dirs
* bus/config-parser.c (struct BusConfigParser): Add conf_dirs list
(merge_included): Also merge conf_dirs list
(bus_config_parser_unref): Clear conf_dirs list
(include_dir): Add directory to conf_dirs list
(bus_config_parser_get_conf_dirs): New function
* bus/dir-watch.[ch]: New files
* bus/Makefile.am (BUS_SOURCES): Add dir-watch.[ch]
* configure.in: Add checks for D_NOTIFY on Linux
