libgloss: doc: fix dir info entry usage

Wrapping the dir info with @ifnottex means it's included in all other
outputs like html which makes no sense.  Switch to @direntry which is
specific for this content and is automatically written to the output
that makes sense, and omitted from the rest.

libgloss/doc/porting.texi

@@ -43,12 +43,13 @@ Permission is granted to copy and distribute translations of this manual
 into another language, under the above conditions for modified versions.
 @end titlepage
 
-@ifnottex
-@format
+@direntry
 START-INFO-DIR-ENTRY
 * Embed with GNU: (porting-).         Embed with GNU
 END-INFO-DIR-ENTRY
-@end format
+@end direntry
+
+@ifnottex
 Copyright (c) 1993, 1994, 1995 Cygnus Support
 
 Permission is granted to make and distribute verbatim copies of