Various fixes

Hi,
to give some more insight of the commit: We are using your library to communicate with RabbitMQ in our Qt-based software. In order to make it work for our purposes we had to do some behavioral as well as some performance fixes. We're always compiling with warnings as errors, hence we had to fix some warnings that GCC 4.6 spit out. Furthermore, I changed the communication from the network with other components to be based on callbacks and not SIGNAL/SLOT's because this didn't scale to many channels (since every channel object's slot was called for an incoming message, and not only the one with the desired channel number). I also rewrote the main networking code to something that is slightly simpler since it keeps less state, because we observed some bugs where the buffers would fill up infinitely. I think the new code can still be improved and simplified, but it seems to work and be relatively efficient.

Btw, you are using some specific codepage for Russian(?) characters and it might be a good idea to convert all the files to UTF-8 (or - even better - to re-write the comments in English :) ) to make it more accessible.