Added missing prototypes for zlog class
Added further prototype to zlog
Fixed memory leak on zmq_sendmsg failure

- when this call fails, caller has to use zmq_msg_close() to
  avoid memory leak on messages larger than 30 bytes
Relicensed CZMQ to MPLv2

- fixed all source file headers
- removed COPYING/COPYING.LESSER with GPLv3 and LPGv3 + exceptions
- added LICENSE with MPLv2 text
- removed ztree class, which cannot be relicensed
- (that should be reintroduced as foreign code, wrapped in CZMQ code)
Regenerated build scripts
Merge pull request #427 from hintjens/master

Added missing prototypes for zlog class