Pdo: Document Pdo\Dblib::ATTR_DATETIME_CONVERT (#4658)

* Document Pdo\Dblib::ATTR_DATETIME_CONVERT

Author: NattyNarwhal

reference/pdo_dblib/pdo-dblib.xml

@@ -142,6 +142,13 @@
      <term><constant>Pdo\Dblib::ATTR_DATETIME_CONVERT</constant></term>
      <listitem>
       <simpara>
+       This connection attribute controls the format of strings for datetime
+       types. When this is &false;, PDO_DBLIB will return a datetime type as a
+       string in the format that SQL Server returns it in (i.e.
+       <literal>"2017-10-27 10:22:44"</literal>). When &true;, PDO_DBLIB will
+       convert the datetime type into a string using a user-defined or locale
+       format, as specified in the FreeTDS <filename>locales.conf</filename>
+       file. By default, this attribute is &false;.
       </simpara>
      </listitem>
     </varlistentry>