README.md: update gnu directory description

(At this point in main we have just LGPL libdialog and dialog, and GPL
diff3, left in gnu/.)

Reported by:	bapt
MFC after:	3 days
Sponsored by:	The FreeBSD Foundation

(cherry picked from commit 266cbbfc65263a3b8bc7c95dd3d589aab7cefe7f)

README

@@ -35,8 +35,9 @@ crypto		Cryptography stuff (see crypto/README).
 
 etc		Template files for /etc.
 
-gnu		Various commands and libraries under the GNU General Public
-		License.  Please see gnu/COPYING* for more information.
+gnu		Commands and libraries under the GNU General Public License
+		(GPL) or Lesser General Public License (LGPL).  Please see
+		gnu/COPYING* for more information.
 
 include		System include files.
 

README.md

@@ -37,8 +37,9 @@ crypto		Cryptography stuff (see crypto/README).
 
 etc		Template files for /etc.
 
-gnu		Various commands and libraries under the GNU Public License.
-		Please see gnu/COPYING* for more information.
+gnu		Commands and libraries under the GNU General Public License
+		(GPL) or Lesser General Public License (LGPL).  Please see
+		gnu/COPYING* for more information.
 
 include		System include files.