Camera button support: make it actually work

Previous commits were merged so fast that I didn't even
added the code that actually DOES launch the camera.
Let me fix that.

Change-Id: I4fcb3c46e5fd50e273dcf19fd3eb35a3f9d979e0

Conflicts:

	core/java/android/provider/Settings.java
	policy/src/com/android/internal/policy/impl/PhoneWindowManager.java