doc: Remove redundant duplicate URLs from ulink elements

Empty ulink elements default to displaying the URL, so there is no need
to specify the URL again.  This was already done for most occurrences,
but some cases didn't follow this convention.

doc/src/sgml/external-projects.sgml

@@ -65,42 +65,42 @@
       <entry>DBD::Pg</entry>
       <entry>Perl</entry>
       <entry>Perl DBI driver</entry>
-      <entry><ulink url="http://search.cpan.org/dist/DBD-Pg/">http://search.cpan.org/dist/DBD-Pg/</ulink></entry>
+      <entry><ulink url="http://search.cpan.org/dist/DBD-Pg/"></ulink></entry>
      </row>
 
      <row>
       <entry>JDBC</entry>
       <entry>JDBC</entry>
       <entry>Type 4 JDBC driver</entry>
-      <entry><ulink url="http://jdbc.postgresql.org/">http://jdbc.postgresql.org/</ulink></entry>
+      <entry><ulink url="http://jdbc.postgresql.org/"></ulink></entry>
      </row>
 
      <row>
       <entry>libpqxx</entry>
       <entry>C++</entry>
       <entry>New-style C++ interface</entry>
-      <entry><ulink url="http://pqxx.org/">http://pqxx.org/</ulink></entry>
+      <entry><ulink url="http://pqxx.org/"></ulink></entry>
      </row>
 
      <row>
       <entry>Npgsql</entry>
       <entry>.NET</entry>
       <entry>.NET data provider</entry>
-      <entry><ulink url="http://www.npgsql.org/">http://www.npgsql.org/</ulink></entry>
+      <entry><ulink url="http://www.npgsql.org/"></ulink></entry>
      </row>
 
      <row>
       <entry>pgtclng</entry>
       <entry>Tcl</entry>
       <entry></entry>
-      <entry><ulink url="http://sourceforge.net/projects/pgtclng/">http://sourceforge.net/projects/pgtclng/</ulink></entry>
+      <entry><ulink url="http://sourceforge.net/projects/pgtclng/"></ulink></entry>
      </row>
 
      <row>
       <entry>psqlODBC</entry>
       <entry>ODBC</entry>
       <entry>ODBC driver</entry>
-      <entry><ulink url="https://odbc.postgresql.org/">https://odbc.postgresql.org/</ulink></entry>
+      <entry><ulink url="https://odbc.postgresql.org/"></ulink></entry>
      </row>
 
      <row>
@@ -172,43 +172,43 @@
      <row>
       <entry>PL/Java</entry>
       <entry>Java</entry>
-      <entry><ulink url="https://github.com/tada/pljava">https://github.com/tada/pljava</ulink></entry>
+      <entry><ulink url="https://github.com/tada/pljava"></ulink></entry>
      </row>
 
      <row>
       <entry>PL/PHP</entry>
       <entry>PHP</entry>
-      <entry><ulink url="http://www.commandprompt.com/community/plphp/">http://www.commandprompt.com/community/plphp/</ulink></entry>
+      <entry><ulink url="http://www.commandprompt.com/community/plphp/"></ulink></entry>
      </row>
 
      <row>
       <entry>PL/Py</entry>
       <entry>Python</entry>
-      <entry><ulink url="http://python.projects.postgresql.org/backend/">http://python.projects.postgresql.org/backend/</ulink></entry>
+      <entry><ulink url="http://python.projects.postgresql.org/backend/"></ulink></entry>
      </row>
 
      <row>
       <entry>PL/R</entry>
       <entry>R</entry>
-      <entry><ulink url="http://www.joeconway.com/plr/">http://www.joeconway.com/plr/</ulink></entry>
+      <entry><ulink url="http://www.joeconway.com/plr/"></ulink></entry>
      </row>
 
      <row>
       <entry>PL/Ruby</entry>
       <entry>Ruby</entry>
-      <entry><ulink url="http://raa.ruby-lang.org/project/pl-ruby/">http://raa.ruby-lang.org/project/pl-ruby/</ulink></entry>
+      <entry><ulink url="http://raa.ruby-lang.org/project/pl-ruby/"></ulink></entry>
      </row>
 
      <row>
       <entry>PL/Scheme</entry>
       <entry>Scheme</entry>
-      <entry><ulink url="http://plscheme.projects.postgresql.org/">http://plscheme.projects.postgresql.org/</ulink></entry>
+      <entry><ulink url="http://plscheme.projects.postgresql.org/"></ulink></entry>
      </row>
 
      <row>
       <entry>PL/sh</entry>
       <entry>Unix shell</entry>
-      <entry><ulink url="https://github.com/petere/plsh">https://github.com/petere/plsh</ulink></entry>
+      <entry><ulink url="https://github.com/petere/plsh"></ulink></entry>
      </row>
     </tbody>
    </tgroup>

doc/src/sgml/runtime.sgml

@@ -1428,7 +1428,7 @@ $ <userinput>sysctl -w vm.nr_hugepages=3170</userinput>
    <para>
     For a detailed description of the <productname>Linux</productname> huge
     pages feature have a look
-    at <ulink url="https://www.kernel.org/doc/Documentation/vm/hugetlbpage.txt">https://www.kernel.org/doc/Documentation/vm/hugetlbpage.txt</ulink>.
+    at <ulink url="https://www.kernel.org/doc/Documentation/vm/hugetlbpage.txt"></ulink>.
    </para>
 
   </sect2>