Optionally enable keepalive on the socket

Keepalive actively checks that the other end of the connection is still
open, and prevents blocking forever on half-open connections.
Merge pull request #187 from arnaud-lb/keepalive

Optionally enable keepalive on the socket
Signals not handled when the queue is empty
Signals not handled when the queue is empty
Merge pull request #188 from dmikhinev/master

Signals not handled when the queue is empty
Replace not operator per "Identical" operator

AMQPChannel "__destruct" function was issuing a Segmentation Fault error
and changing the operators will make the error stop.
Merge pull request #189 from nelsonsar/change_amqpchannel_logical_operators

Replace not operator per "Identical" operator
Fix: avoid losing message meta-data because of weak type evaluation