Flush identity message for inproc transport

The scoket implementation for inproc transfer failed to flush
identity message. The result was that the identity message
was not delivered until after the user sent the first message.

The identity message was never delivered if the user
used the socket only to receive messages.

Fixed issue #351

Fix error in router socket introduced in the previous commit

router: always respect message boundaries

router: reimplement peer identification

The current implementaion of router socket does not
handle the full pipe and unroutable messages properly.
Namely, in those cases, the socket could route some
message parts into a wrong connection.

The new implementation allows one to send messages through
a router socket to a peer even before receiving
messages from this peer.

Fixes issue #304

Added checking to zmq_ctx_set()

Fixed issue (unknown) on zmq_init(-1)

Code cleanup

Fix return value of send for router socket

It is the job of the posix_assert macro to check
the value. No need to do it twice.

The patch also fixes some whitespace problems.

The method is not used anymore.

The check_write method does not use the passed message.
The parameter was needed to implement the swap.
As the swap is not supported anymore, it is safe to remove this parameter.

Tcp address fixes anc cleanups

This still rejects 00 as port number.

Fixed issue LIBZMQ-348 - Valgrind support

Fix for issue #307

Don't set the AI_V4MAPPED flag on FreeBSD

The problem is that even though the AI_V4MAPPED flag is defined
on FreeBSD, the getaddrinfo function does not support it and
returns EAI_BADFLAGS.

The patch also sets the flag on Windows if it is defined there.
This is true for Windows Vista and later.

Fixes issue #331.

Fixed issue #334

dist was skipping over pipes when one failed because the non-working pipe got
swapped with a working pipe but the write was never retried on that pipe

Fixed issue #325

Makefile.am wasn't fixed, so libzmq was not building

Mark sockets as invalid when closed, not reaped

Previously, sockets were still "valid" after being closed and only marked
as invalid when destroyed. This meant programs could access closed sockets.
Now the socket is marked "invalid" when closed.

Completed internal renaming of XREP/XREQ to ROUTER/DEALER