Add back httptask support for osx.

Hey.

Tried the osx build to run my game (instead of the 1.4 release) but found out that I was no longer able to use MOAIHttpTask. After a good tip from @halfnelson in IRC it seems that this does the trick.

This PR is into master, but master won't build at all on my osx. I built it using the 1.5-stable branch. Not sure how you would rather have this submitted?

Anyway, MOAI also crashes after a couple of seconds in 1.5, but that is probably for another issue.

Let me know if I should submit the PR in some other way, or anything else I can do to help.