Added "Fall through" comments to some switch statements where multiple

approaches are tried in order to prevent warnings from GCC 7 (and newer).

Added includes on Linux for sys/sysmacros.h as the old defines in
the sys/types.h file will be removed in the future.

src/init.c

@@ -1318,6 +1318,7 @@ void startup(CHILD *ch)
 		case POWERFAIL:
 		case ONCE:
 			if (ch->flags & XECUTED) break;
+                        /* Fall through */
 		case ONDEMAND:
 		case RESPAWN:
   			ch->flags |= RUNNING;