README.developer: restore libtool prerequisite text

git-svn-id: https://hamlib.svn.sourceforge.net/svnroot/hamlib/trunk@3050 7ae35d74-ebe9-4afe-98af-79ac388436b8

README.developer

@@ -181,9 +181,7 @@ that need to be installed manually.
 * libtool       2.2.6b                      # libtool --version
 * svn for connection to hamlib.svn.sourceforge.net
 
-N.B. Hamlib no longer supports versions of libtool earlier than 2.2.6b in
-compliance with CVE-2009-3736.  If an older version is found, Hamlib will use
-the bundled libtool 2.2.6b instead.
+N.B. Hamlib requires libtool >= 2.2.6b in compliance with CVE-2009-3736.
 
 Optional, but highly recommended:
 * GNU C++                           # g++ --version