Remove netkey directory from cscope/TAGs generation and replace

it with netipsec now that KAME IPsec is gone.
While here add missing netinet6 directories.

Add comments about the ports needed to be able to run those targets.

Reviewed by:	philip
Approved by:	re (rwatson)

sys/Makefile

@@ -10,7 +10,7 @@ SUBDIR=	boot
 # Directories to include in cscope name file and TAGS.
 CSCOPEDIRS=	bsm cam coda compat conf contrib crypto ddb dev fs geom gnu \
 		i4b isa kern libkern modules net net80211 netatalk netatm \
-		netgraph netinet netinet6 netipx netnatm netncp \
+		netgraph netinet netinet6 netipsec netipx netnatm netncp \
 		netsmb nfs nfsclient nfs4client rpc pccard pci security sys \
 		ufs vm ${ARCHDIR}
 
@@ -24,12 +24,14 @@ SUBDIR+=modules
 
 HTAGSFLAGS+= -at `awk -F= '/^RELEASE *=/{release=$2}; END {print "FreeBSD", release, "kernel"}' < conf/newvers.sh`
 
+# You need the devel/cscope port for this.
 cscope:	${.CURDIR}/cscopenamefile
 	cd ${.CURDIR}; cscope -k -p4 -i cscopenamefile
 
 ${.CURDIR}/cscopenamefile: 
 	cd ${.CURDIR}; find ${CSCOPEDIRS} -name "*.[csh]" > ${.TARGET}
 
+# You need the devel/global and one of editor/emacs* ports for that.
 TAGS ${.CURDIR}/TAGS:	${.CURDIR}/cscopenamefile
 	rm -f ${.CURDIR}/TAGS
 	cd ${.CURDIR}; xargs etags -a < ${.CURDIR}/cscopenamefile

sys/kern/Make.tags.inc

@@ -43,8 +43,9 @@ COMM=	${SYS}/dev/advansys/*.[ch] \
 	${SYS}/netatalk/*.[ch] \
 	${SYS}/netatm/*.[ch] \
 	${SYS}/netinet/*.[ch] \
+	${SYS}/netinet6/*.[ch] \
+	${SYS}/netipsec/*.[ch] \
 	${SYS}/netipx/*.[ch] \
-	${SYS}/netkey/*.[ch] \
 	${SYS}/netnatm/*.[ch] \
 	${SYS}/nfs/*.[ch] \
 	${SYS}/nfsclient/*.[ch] \
@@ -61,8 +62,9 @@ COMMDIR1= ${SYS}/conf \
 	${SYS}/netatalk \
 	${SYS}/netatm \
 	${SYS}/netinet \
+	${SYS}/netinet6 \
+	${SYS}/netipsec \
 	${SYS}/netipx \
-	${SYS}/netkey \
 	${SYS}/netnatm \
 	${SYS}/nfs \
 	${SYS}/pci \