check-missing-updates.sh: Clarify what needs to be done when there is an issue

scripts/check-missing-updates.sh

@@ -11,9 +11,13 @@ git diff > diff_check
 WC=`cat diff_check | wc -l`
 if [ $WC != 0 ] ; then
 	echo
-	echo "Please correct the following files that were changed by"
-	echo "./configure (by updating its master file)"
-	echo "or 'make update-map-file'."
+	echo "Please update the master file (usually .in) for the following files"
+	echo "that had the changes reverted by the running of './configure'."
+	echo "There is no need to update the original files, just commit the"
+	echo "changed .in files."
+	echo
+	echo "Or run 'make update-map-file' and commit the changes to"
+	echo "libcoap-3.map and libcoap-3.sym."
 	echo
 	cat diff_check
 	exit 1