Make the DAAP protocol parsing in Amarok more robust

The Firefly version installed on my Readynas Duo (Radiator 4.1.7) sends the
aeMK (mediakind) field as an 32 bit int instead of a 8 bit char.

Amarok currently only consumes one byte instead of four, despite the fact that
the field length is correctly reported as four bytes by the server. The
attached patch reworks the DAAP protocol parsing to be more robust.

Courtesy Lukas Sandström