Changes to netmask.rb for AIX

The changes included are to accommodate the netmask fact in AIX systems.  Looks like there's been some considerable changes to the ipconfig parts of the code, I attempted to make some small change there.  Basically, the regex formats for AIX are identical to SunOS.  The real difference between the two is the path to the command.  In the case of AIX, it is /etc/ifconfig -a.