[Bug Fix] Workaround libev bug.

On OSX EV_ERROR declared in `ev.h` conflicts with that declared in `/usr/include/sys/event.h`.
http://stackoverflow.com/questions/16660816/libev-4-15-doesnt-compile-on-osx-10-8
Merge pull request #12 from 3Hren/bugfix-MacBuild

[Bug Fix] Workaround libev bug.