Move ddb.conf to sbin/ddb/ and switch to CONFS.

This helps pkgbase as this config file will now be tagged as a config file.

Approved by:	allanjude (mentor)
Differential Revision:	https://reviews.freebsd.org/D16675

etc/Makefile

@@ -15,7 +15,6 @@ SUBDIR+=sendmail
 BIN1=	crontab \
 	devd.conf \
 	devfs.conf \
-	ddb.conf \
 	dhclient.conf \
 	disktab \
 	fbtab \

sbin/ddb/Makefile

@@ -1,5 +1,6 @@
 # $FreeBSD$
 
+CONFS=	ddb.conf
 PACKAGE=runtime
 PROG=	ddb
 SRCS=	ddb.c ddb_capture.c ddb_script.c