Fix: "mysql --xml" now print NULL values the same way that "mysqldump --xml" does:
<field name="name" xsi:nil="true" />
to distinguish from empty strings:
<field name="name"></field>
and from string "NULL":
<field name="name">NULL</field>
tool does, with the column names as attributes on <field>
elements, instead of trying to use the column name as the
element name. Also fix some encoding issues. (Bug #7811)
