update Makefile with ztree.o
Merge remote-tracking branch 'upstream/master'
Merge remote-tracking branch 'upstream/master'
Merge remote-tracking branch 'upstream/master'
Merge remote-tracking branch 'upstream/master'
Merge remote-tracking branch 'upstream/master'
bugfix: leaking sockets list, sndhwm/rcvhwm not shadow copied
Merge pull request #249 from pijyoi/master

bugfixes to zctx.c