newvers.sh: consider as modified SVN mixed revision and other cases

The newvers -R option is intended to include build metadata (e.g. user,
host, time) if the build is from an unmodified VCS tree. For subversion
it considered a trailing 'M' as an indication of a modified tree, and
any other version string as modified.

Also include mixed revision checkouts (e.g. 123:126), switched (123S)
and partial (123P) working copies as modified: the revision number is
insufficient to uniquely determine which source was used for the build.

Reported by:	gjb
Reviewed by:	gjb
MFC after:	1 month
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D8853

sys/conf/newvers.sh

@@ -197,12 +197,17 @@ fi
 
 if [ -n "$svnversion" ] ; then
 	svn=`cd ${SYSDIR} && $svnversion 2>/dev/null`
-	if expr "$svn" : ".*M" >/dev/null; then
-		modified=true
-	fi
 	case "$svn" in
-	[0-9]*)	svn=" r${svn}" ;;
-	*)	unset svn ;;
+	[0-9]*[MSP]|*:*)
+		svn=" r${svn}"
+		modified=true
+		;;
+	[0-9]*)
+		svn=" r${svn}"
+		;;
+	*)
+		unset svn
+		;;
 	esac
 fi
 
@@ -270,7 +275,7 @@ if [ -n "$hg_cmd" ] ; then
 fi
 
 include_metadata=true
-while getopts r opt; do
+while getopts rR opt; do
 	case "$opt" in
 	r)
 		include_metadata=