Correct the documented default of the http follow_location option (#5845)

Not setting the option and setting it to 1 are not equivalent. When it is absent, redirects are only followed for the 300, 301, 302, 303, 307 and 308 response codes; when it is set, any response carrying a Location header is followed regardless of its response code.

Author: lacatoire

language/context/http.xml

@@ -128,9 +128,14 @@
        Follow <literal>Location</literal> header redirects. Set to
        <literal>0</literal> to disable.
       </para>
-      <para>
-       Defaults to <literal>1</literal>.
-      </para>
+      <simpara>
+       When this option is not set, redirects are only followed for the
+       <literal>300</literal>, <literal>301</literal>, <literal>302</literal>,
+       <literal>303</literal>, <literal>307</literal> and <literal>308</literal>
+       response codes. Setting it to <literal>1</literal> is not equivalent:
+       any response carrying a <literal>Location</literal> header is then
+       followed, whatever its response code.
+      </simpara>
      </listitem>
     </varlistentry>
     <varlistentry xml:id="context.http.max-redirects">