Fix autogen flag about obsolete directive name
Added ZMQ_BUILD_TESTS to CMakeLists.txt to allow turning off tests. Useful when building ZMQ as a git submodule.
Merge pull request #874 from gyulalaszlo/cmake-switchable-tests

Added ZMQ_BUILD_TESTS to CMakeLists.txt to allow turning off tests.
Merge branch 'master' of github.com:zeromq/libzmq
Merge branch 'master' of github.com:jimrthy/libzmq