Review of 3482

Thank you for working on this. I merged the master branch back in, tweaked a few small things, and had a specific concern about the short-circuiting of the OS X generate() call in lib/msf/core/payload/osx.rb.

Can you take a look at this short-circuit use of:
```
 #
  # Overload the generate() call to prefix our stubs
  #
  def generate(*args)
    return generate_macho
```

The generate_macho() method does nothing and it is bypassing all of the argument processing that seems quite important for things like PrependSetuid support.