Use the new ?= operator to set the on_panic value for the optional ddb

hierachie.

etc/sysctl.conf

@@ -1,6 +1,6 @@
 #!/sbin/sysctl -f
 #
-# $NetBSD: sysctl.conf,v 1.6 2009/03/11 23:22:57 martin Exp $
+# $NetBSD: sysctl.conf,v 1.7 2009/04/01 16:20:55 martin Exp $
 #
 # sysctl(8) variables to set at boot time.
 
@@ -10,7 +10,7 @@
 # at the db> prompt.
 # If you understand the implication and want to change the behaviour before
 # /etc/rc.d/sysctl is run, use the kernel option DDB_ONPANIC, see options(4).
-ddb.onpanic=0
+ddb.onpanic?=0
 
 # Default core name template:
 #kern.defcorename=%n.core