Add blank lines around Configure's duplicate extension diagnostic.

The diagnostic message containing the duplicate extension did not stand out,
particularly given that the immediately previous output is a very long line
of found extensions. So add blank lines on either to make it easier to
spot.

diff --git a/Configure b/Configure
index 347bfee..43f56bf 100755 (executable)
--- a/Configure
+++ b/Configure
@@ -22182,6 +22182,7 @@ find_extensions='
            else
                echo " $known_extensions $nonxs_extensions" > $$.tmp;
                if $contains " $this_ext " $$.tmp; then
+                   echo >&4;
                    echo "Duplicate directories detected for extension $xxx" >&4;
                    echo "Configure cannot correctly recover from this - shall I abort?" >&4;
                    case "$knowitall" in
@@ -22191,7 +22192,8 @@ find_extensions='
                    . ../UU/myread;
                    case "$ans" in
                    n*|N*) ;;
-                   *) echo "Ok.  Stopping Configure." >&4;
+                   *) echo >&4;
+                      echo "Ok.  Stopping Configure." >&4;
                       echo "Please remove the duplicate directory (eg using git clean) and then re-run Configure" >&4;
                        exit 1;;
                    esac;