Samsung STK: Add USSD support

Allow USSD-based STK applications to work

Change-Id: I483f37a44a6c3ed43eefcf979e17b84877d03f93

Conflicts:
	src/java/com/android/internal/telephony/cat/CatService.java

Conflicts:
	src/java/com/android/internal/telephony/cat/CatService.java