Driver support for creating allocations from a Script

Bug: 23535985

Implement functions rsCreateElement, rsCreateType and rsCreateAllocation
in libRSDriver to allow creation of Allocations from a Script.

In its current state, the RS objects returned from these functions are
guaranteed to leak due to incorrect handling of their reference counts.
They'll be fixed in a follow-up CL.

Change-Id: I9bb7c72a8dd3cd1aac2de3bad92276c3af662484
4 files changed