Fix Support For Mac OS 

In this project, there are various points where the OS of the machine is checked first before making system calls. The major problem is that POSIX macro is being checked as well as WIN32, however, Mac OS does not define either of these macros. Mac OS defines __APPLE__ macro. 

This issue can be fixed by having an #elseif __APPLE__ in places where system calls are necessary for Omega. 