Refactoring of nn_msgpipe class

Signed-off-by: Martin Sustrik <sustrik@250bpm.com>
Couple of fixes to refactored inproc transport

Signed-off-by: Martin Sustrik <sustrik@250bpm.com>
Multiple problems with inproc shutdown fixed

Signed-off-by: Martin Sustrik <sustrik@250bpm.com>