* Added a version.sh and relevant changes to configure.in to extract the API
  version from zmq.h at the time autogen.sh is run.
* Moved the version macros to be next to zmq_version in zmq.h and improved
  the comments.
* Modified ZMQ_MAKE_VERSION to use (x) instead of plain x when expanding
  macro parameters.
Signed-off-by: Martin Lucina <mato@kotelna.sk>