Problem: can't build czmq on osx (#1835)
Problem: can't build czmq on osx (#1835)

* Problem: can't build czmq on osx

Solution: use _NSGetEnviron () routine to get environ variable on OSX

* Problem: still not build on osx

Solution: fix return type of _NSGetEnviron

* Problem: zproc.c does not build on Linux

Solution: declare extern char **environ

* Problem: environ not declared in Travis

Solution: streamline the code

1.) use _NSGetEnviron on OSX
2.) declare extern har **environ for other nixes

* Problem: environ not compile time constant

Solution: use macro as gstreamer
http://gstreamer-devel.966125.n4.nabble.com/NSGetEnviron-in-use-by-glib-genviron-for-iOS-arm-td4665089.html

zeromq/czmq,opedroso/czmq,zeromq/czmq,opedroso/czmq,opedroso/czmq,zeromq/czmq,opedroso/czmq,opedroso/czmq,opedroso/czmq,opedroso/czmq,opedroso/czmq,zeromq/czmq,zeromq/czmq,zeromq/czmq,zeromq/czmq,opedroso/czmq,zeromq/czmq