Move back group, master.passwd and shells to etc directory

Use the .PATH mechanism instead so keep installing them from lib/libc/gen

While here revert 347961 and 347893 which are no longer needed

Discussed with:	manu
Tested by:	manu
ok manu@

UPDATING

@@ -31,12 +31,6 @@ NOTE TO PEOPLE WHO THINK THAT FreeBSD 13.x IS SLOW:
 	disable the most expensive debugging functionality run
 	"ln -s 'abort:false,junk:false' /etc/malloc.conf".)
 
-20190517:
-	For users of mergemaster, after recent changes to locations of
-	master.passwd and group in the source tree mergemaster needs to be
-	updated.  Before running `mergemaster -p', cd to usr.sbin/mergemaster
-	and run `make install'.
-
 20190513:
 	User-wired pages now have their own counter,
 	vm.stats.vm.v_user_wire_count.  The vm.max_wired sysctl was renamed

lib/libc/gen/Makefile.inc

@@ -2,7 +2,7 @@
 # $FreeBSD$
 
 # machine-independent gen sources
-.PATH: ${LIBC_SRCTOP}/${LIBC_ARCH}/gen ${LIBC_SRCTOP}/gen
+.PATH: ${LIBC_SRCTOP}/${LIBC_ARCH}/gen ${LIBC_SRCTOP}/gen ${SRCTOP}/etc
 
 CONFS+=	group master.passwd shells
 CONFSMODE_master.passwd=	600

usr.sbin/etcupdate/etcupdate.sh

@@ -1737,9 +1737,7 @@ WARNINGS=$WORKDIR/warnings
 EDITOR=${EDITOR:-/usr/bin/vi}
 
 # Files that need to be updated before installworld.
-PREWORLD_FILES="lib/libc/gen/master.passwd lib/libc/gen/group"
-# If on an older tree, use it instead.  Delete after 13.0.
-[ -f ${SRCDIR}/etc/master.passwd ] && PREWORLD_FILES="etc/master.passwd etc/group"
+PREWORLD_FILES="etc/master.passwd etc/group"
 
 # Handle command-specific argument processing such as complaining
 # about unsupported options.  Since the configuration file is always

usr.sbin/mergemaster/mergemaster.sh

@@ -669,12 +669,9 @@ case "${RERUN}" in
     ;;
   *)
     # Only set up files that are crucial to {build|install}world
-    { MM_PASSDIR="${SOURCEDIR}/lib/libc/gen"
-      # If on an older tree, use it instead.  Delete after 13.0.
-      [ -f ${SOURCEDIR}/etc/master.passwd ] && MM_PASSDIR="${SOURCEDIR}/etc"
-      mkdir -p ${TEMPROOT}/etc &&
-      cp -p ${MM_PASSDIR}/master.passwd ${TEMPROOT}/etc &&
-      install -p -o root -g wheel -m 0644 ${MM_PASSDIR}/group ${TEMPROOT}/etc;} ||
+    { mkdir -p ${TEMPROOT}/etc &&
+      cp -p ${SOURCEDIR}/etc/master.passwd ${TEMPROOT}/etc &&
+      install -p -o root -g wheel -m 0644 ${SOURCEDIR}/etc/group ${TEMPROOT}/etc;} ||
     { echo '';
       echo '  *** FATAL ERROR: Cannot copy files to the temproot environment';
       echo '';