Fix compilation on windows using msys2

Problem: GCC 6 build fails due to misleading indentation and visually ambiguous if/else block ordering.

Solution: fixed indentation and if/else block.

RELICENSE: William Swanson

Critical BUG introduced with #2518 fixed.

Problem: Bad style in tcp.hpp/cpp

Solution: Add spaces between function
name and parentheses.

Another macro correction.

Consistency of Windows TCP tuning assertions

Treat ECONNRESET, ENETRESET and EINTR as non-fatal
failures in TCP Tuning on Windows as they are in the
Unixes.  Also adds ENETRESET to the Unix list that was missing.

Case found not covered in latest zmq::proxy() code.

Relicense: Tom Whittock grant

Reworked zmq::proxy() for improved performance.

adding licence

re-enable AI_V4MAPPED on FreeBSD & DragonFlyBSD

fix a typo - assigment was used instead of comparison

Detect AI_V4MAPPED is not supported in getaddrinfo() on the fly
and retry query. This issue was seen on ancient FreeBSD releases
and current implementation does support this flag correctly.

choose IP(v6) address based on ipv6_ flag in a correct way

* Relicense Grant - Thomas Rodgers (rodgert@twrodgers.com)

Add relicense grant for eburkitt

Problem: typos in RELICENSE/ptroja.md

cmake: Use LOCATION property only for imported targets

Newer CMake versions allow use of the LOCATION target property only for
imported targets (CMP0026). Because the old package variables are only
needed for backward compatibility after configuration they could be
deactivated for super projects which build ZeroMQ together with other
projects.
Signed-off-by: Stefan Herbrechtsmeier <stefan.herbrechtsmeier@weidmueller.com>