Include the post requires until #2354 lands

Another one that needs the manual require. See #2354, which will solve this once and for all on Sep 24,2013.

In the meantime, **please** ensure that if you're using `Msf::Post` mixins, you require the appropriate mixin **in the module**.

## Verification

Set up a test branch. Don't ever land this branch upstream since it's destructive.

 - [ ] `git checkout upstream-master`
 - [ ] `git checkout -b test-2354` # Don't land this branch since you're deleting stuff.
 - [ ] `git rm -rf modules/post/*`
 - [ ] `git commit -m "Never land this"

Test the failure condition:

 - [ ] `git checkout upstream-master modules/exploits/windows/local/ms13_005_hwnd_broadcast.rb`
 - [ ] See the error on loading as reported by d0rmous3: http://pastebin.com/8XaJxbdz

Test the fix:

 - [ ] `git checkout upstream/pr/XXXX modules/exploits/windows/local/ms13_005_hwnd_broadcast.rb`
 - [ ] See no error.
 - [ ] Get info on the module: `msf > info exploit/windows/local/ms13_005_hwnd_broadcast `

Switch back to master, and then land this PR as normal.