Validate context when using RS objects.

graphics/java/android/renderscript/Allocation.java

graphics/java/android/renderscript/AllocationAdapter.java

graphics/java/android/renderscript/BaseObj.java

graphics/java/android/renderscript/Element.java

graphics/java/android/renderscript/FieldPacker.java

graphics/java/android/renderscript/FileA3D.java

graphics/java/android/renderscript/Mesh.java

graphics/java/android/renderscript/Path.java

graphics/java/android/renderscript/Program.java

graphics/java/android/renderscript/ProgramFragment.java

...va/android/renderscript/ProgramFragmentFixedFunction.java

graphics/java/android/renderscript/ProgramVertex.java

...java/android/renderscript/ProgramVertexFixedFunction.java

graphics/java/android/renderscript/RenderScript.java

graphics/java/android/renderscript/Script.java

graphics/java/android/renderscript/Type.java