Set the ZMQ_HEARTBEAT_TIMEOUT to default to the value of
ZMQ_HEARTBEAT_IVL if it's not explicitly set.
Change the units of ZMQ_HEARTBEAT_TTL to milliseconds in the API
and round down to the nearest decisecond so that all the options
are using the same units.
Make the maximum heartbeat TTL match the spec (6553 seconds)

Add documentation for ZMTP heartbeats/fix test

Add ZMTP connection heartbeats

This commit adds ZMTP connection heartbeats described in
http://rfc.zeromq.org/spec:37/ZMTP.

Typo fix

Problem: zmq::socket_base_t::connect fails on tcp ipv6 address

Rebase3

The shared reference count was not shared but copied. msg_t cannot
store the refcnt itsef but has to store a pointer to an externally
allocated (shared) refcnter. The changes to lmsg are reverted to
use content_t again. Howver, this introduces an allocation in v2_decoder
when creating the message which can be avoided. When allocating the reception
buffer, space is allocated for the maximum number of reference counts
(8192 / max_vsm_size = 8192/64 = 128 zmq:atomic_counter objects). This
increases the buffer by 128*sizeof(atomic_counter) = 128*4 = 512 bytes only.
When creating a message, the refcnt member is set to the address of one of the
pre-allocated atomic_counter_t objects. To do so, a new msg_t type zcmsg
is introduced because msg::copy must discriminate between the message types
when releasing memory.

zero-copy msg_t::init cannot be used when the message exceeds either
the buffer end or the last received byte. To detect this, the buffer
is now resized to the numnber of received bytes.

Probably fix build issue on Solaris.

See #1220 recent comments. This change is untested yet seems
safe.

Problem: 4.1 broke the ABI yet did not bump ABI number

Solution: bump to ABI version 5

Fix windows build

test zmq_msg custom free-function

new allocation caused reference counters to lose track on copy

don't check POLLOUT for single-socket proxies

Fix initialization order.

Fixes #1431.

Enable install of man pages when BUILD_DOC is not set by shifting INS…

Enable install of man pages when BUILD_DOC is not set by shifting INSTALL_MAN outside of BUILD_DOC's if/endif

Update documentation for zmq_setsockopt.

Pull request #1426 now allow for changing the watermark
after and connect() or a bind(). This patch reflect the
change in the documentation.

Also closes #1416.

Allow changing of high water marks after connection is established

Fixed executable name in the usage string

Fix xpub test to set hwm before bind.

Fail ZMQ_SNDHWM and ZMQ_RCVHWM setsockopt if already connected.