Copy platform.hpp into src directory in cmake build.
Merge branch 'master' of https://github.com/zeromq/libzmq
Revert "Copy platform.hpp into src directory in cmake build."

This reverts commit 11b699e73cbda47ff450554ebca2385d20a0b75a.
Merge branch 'master' of https://github.com/zeromq/libzmq
useless checks were removed
Merge pull request #698 from hashstat/master

Add abstract namespace support for IPC sockets on Linux.
Merge pull request #699 from ezhikus/free_and_delete

It is safe to "free(NULL)" and "delete NULL"
Merge pull request #700 from hashstat/master

Add documentation on Linux ipc abstract namespace support and a bug fix.
Typo in type name "emTPy_slots_t"

https://zeromq.jira.com/browse/LIBZMQ-565
Merge pull request #701 from ezhikus/master

Typo in type name "emTPy_slots_t"
Updated NEWS for 4.0.1 release
Merge pull request #702 from hintjens/master

Updated NEWS for 4.0.1 release
Fixed NEWS for 4.0.1 release
Revert "distinguish between options and defaults"

This reverts commit e7804c5027633d18558c05b550ea11c46fb37c42.
Revert "replace macro constants with enum types for user facing constants"

This reverts commit d4bb6d693f0542bbf35bc1b6810100d5b2a901a8.
Merge pull request #703 from hintjens/master

Reverted use of enums for zmq.h constants (too painful for binding authors)
Update NEWS
Identity can only be set on sockets that can connect to ROUTER
Merge pull request #705 from hintjens/master

Fixed doc for IDENTITY socket option
Rename engine's methods to improve code readability