Added adapters mechanism.

There is two adapters now: usocket(blocking) and
iolib(non-blocking), but it seems like cl+ssl doesn't
work properly with iolib stream sockets, so now
iolib adapter is broken. I'm starting to think about
cl-async-ssl adapter or even maybe about threaded event loop.
Added comments.
Fixed annoying messages on compile time.
Merge branch 'feature-network-adapters'