doc bugfix: ZMQ_MSGMORE should be ZMQ_SNDMORE

Fixed setting TCP keepalive parameters on Windows

Fixes to IPC wildcarding & test cases

- was not waiting long enough at socket close
- increased to 50 msec

Fixed use of deprecated tempnam

add failing test for binding to resources

Update doc for zmq_proxy_steerable [ci skip]

Add tests/test_zap_ipc_creds to .gitignore

Single connect

support signaler_port in config.hpp set to value other than 0 and 5905

tools/: Link curve_keygen with a c++ linker

When trying to linking curve_keygen as if it was a C program, linking
fails (at least with gcc 4.8 on Debian testing) because it can't find
C++ symbols. Linking with g++ instead fixes the issue.

To achieve this, the source is renamed to curve_keygen.cpp, and
tools/Makefile.am is updated accordingly.
Signed-off-by: Gergely Nagy <algernon@balabit.hu>

Add support for extending ZAP request address with IPC peer credentials.

Another take on LIBZMQ-568 to allow filtering IPC connections, this time
using ZAP.  This change is backward compatible.  If the
ZMQ_ZAP_IPC_CREDS option is set, the user, group, and process IDs of the
peer process are appended to the address (separated by colons) of a ZAP
request; otherwise, nothing changes.  See LIBZMQ-568 and zmq_setsockopt
documentation for more information.

Enable building IPC filtering with cmake and another small autoconf fix.

Shortened ZMQ_IPC_ACCEPT_FILTER_[UGP]ID to ZMQ_IPC_FILTER_[UGP]ID.

Fix failing test case in test_filter_ipc.

Add explicit check for primary group.

use enum retired_fd instead of -1

Updated documentation for zmq_disconnect() and zmq_setsockopt().

Add IPC accept filter support

using -1 causes a warning on Windows platform because SOCKET is unsigned.

Adds ZMQ_IPC_ACCEPT_FILTER_{PID,UID,GID} socket options to add processs,
user, and group IDs to the IPC filter sets. Fixes LIBZMQ-568.