Update man page to indicate that --no-hard-links is enabled by on Windows

git-svn-id: http://svn.savannah.nongnu.org/svn/rdiff-backup@927 2b77aa54-bcbc-44c9-a7ec-4f6cf2b41109

trunk/rdiff-backup/rdiff-backup.1

@@ -347,6 +347,8 @@ and take up a bit less space.
 .BI \-\-no-hard-links
 Don't replicate hard links on destination side.  If many hard-linked
 files are present, this option can drastically decrease memory usage.
+This option is enabled by default if the backup source or restore
+destination is running on native Windows.
 .TP
 .B \-\-null-separator
 Use nulls (\\0) instead of newlines (\\n) as line separators, which