Add a direntry to the Rottlog info manual.

diff --git a/doc/rottlog.texi b/doc/rottlog.texi
index 0ba8019..0f29916 100644
--- a/doc/rottlog.texi
+++ b/doc/rottlog.texi
@@ -18,6 +18,11 @@ Documentation License.''
 @end quotation
 @end copying
 
+@dircategory System administration
+@direntry
+* Rottlog: (rottlog).         The GNU log management utility.
+@end direntry
+
 @paragraphindent none
 
 @iftex
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