Modify & update some common files

NOTE:
- Update headers & add kernel-headers + overlays (TeamCanjica's u8500-common)
- RIL: Remove setCurrentPreferredNetworkType() to fix deprecated-override prob.
- RIL: set/getMobileDataEnabled() functionality has moved to TelephonyManager
- RIL: Remove rr.creationTime related code since it's unavailable
- selinux: Remove entry which is also found in external/sepolicy/file_contexts
- selinux: Remove 'system'-related policy (missing in Lollipop)