Add ability to mergemaster to permit the user to type

the absolute path to PAGER if mergemaster can not find
the one already set.

Reviewed by:	mjg
Approved by:	cperciva
MFC after:	2 weeks

usr.sbin/mergemaster/mergemaster.sh

@@ -426,6 +426,8 @@ check_pager () {
     fi
     echo "  Use 'm' to use plain old 'more' as your PAGER for this run"
     echo ''
+    echo "  or you may type an absolute path to PAGER for this run"
+    echo ''
     echo "  Default is to use plain old 'more' "
     echo ''
     echo -n "What should I do? [Use 'more'] "
@@ -451,6 +453,9 @@ check_pager () {
     [mM]|'')
        PAGER=more
        ;;
+    /*)
+       PAGER="$FIXPAGER"
+       ;;
     *)
        echo ''
        echo "invalid choice: ${FIXPAGER}"