Redirect svnversion stderr to /dev/null if we cannot determine

the tree version, for example if the tree is checked out with an
outdated svn from ports, but the base system svnlite is built.

Approved by:	kib (mentor)

sys/conf/newvers.sh

@@ -116,7 +116,7 @@ if [ -d "${SYSDIR}/../.git" ] ; then
 fi
 
 if [ -n "$svnversion" ] ; then
-	svn=`cd ${SYSDIR} && $svnversion`
+	svn=`cd ${SYSDIR} && $svnversion 2>/dev/null`
 	case "$svn" in
 	[0-9]*)	svn=" r${svn}" ;;
 	*)	unset svn ;;