Msg.d

Added POSIX wrapper for <sys/msg.h>

I asked for help on this link: http://forum.dlang.org/thread/lradkwgmyotmldzhynrc@forum.dlang.org and was advised to do a pull request.  This is my first pull request. 
While we at it - is it feasible to move `octal` to `object.d` ? Otherwise it isn't available where it's needed the most.