. DS understands publishing and subscribing where keys are in string

form. Subscriptions are regular expressions.
 . different types are stored per key; currently u32 and/or string.
   the same key can be referenced (publish, subscribe, check) as any type.
 . notify()s are sent when subscriptions are triggered (publishing or
   updating of matching keys); optionally, a subscribe flag sends
   updates for all matching keys at subscription time, instead of only
   after updates after subscribing
 . all interfacing to ds is in /usr/src/lib/syslib/ds.c.
 . subscribe is ds_subscribe
   publish functions are ds_publish_<type>
   retrieve functions are ds_retrieve_<type> (one-time retrieval of a value)
   check functions are ds_check_<type> (check for updated key caller
      subscribes to not yet checked for, or ESRCH for none)
 . ramdisk driver updated with new ds interface

lib/syslib/Makefile.in

@@ -63,6 +63,7 @@ libsys_FILES=" \
 	sys_voutb.c \
 	sys_voutl.c \
 	sys_voutw.c \
-	taskcall.c"
+	taskcall.c \
+	ds.c"
 
 TYPE=both