Fixes make building in OS X:

Fixes make building in OS X:
- Switches default (snapshot) make target to use the Deployment Xcode target
- Makes it possible to jam contribs using make in OS X like is done in Linux
- This means no universal binaries from make, unless "make release" is used. That's the only time it uses the contrib download script. The snapshot target builds contribs locally.

To sum up: this now means that on a Mac, using:
make
....should be functionally equivalent to:
make clean; ./configure; ./jam

git-svn-id: svn://svn.handbrake.fr/HandBrake/trunk@1430 b64f7644-9d1e-0410-96f1-a4d463321fa5