[qmf] Prevents POP3/SMTP incoming data read from stopping when handling large requests.

Keeps reading available data from the socket even if not a entire line is available,
this way readyRead signals will be emitted when new data arrives in the socket.
Merge pull request #42 from nemomobile-packages/popSocket

[qmf] Prevents POP3/SMTP incoming data read from stopping when handling large requests