Fix broken markup, and remove tabs

doc/src/sgml/ref/ecpg-ref.sgml

@@ -145,6 +145,7 @@ PostgreSQL documentation
          Do not use indicators but instead use special values to represent
          NULLs. Historically there have been databases using this approach.
          </para>
+         </listitem>
         </varlistentry>
         <varlistentry>
          <term><option>prepare</option></term>
@@ -154,6 +155,7 @@ PostgreSQL documentation
          prepared statments and reuse a statement if it gets executed again. If the
          cache runs full, libecpg will free the least used statement.
          </para>
+         </listitem>
         </varlistentry>
         <varlistentry>
          <term><option>questionmarks</option></term>
@@ -162,6 +164,7 @@ PostgreSQL documentation
          Allow questionmark as placeholder for compatibility reasons. 
          This used to be the default long ago.
          </para>
+         </listitem>
         </varlistentry>
        </variablelist>
       </para>