Make sure that user-defined bit stays in place when copying function call
nodes, and that mInFunctionWithArrayReturnValue gets reset correctly in
ArrayReturnValueToOutParameter.

BUG=angleproject:971
TEST=WebGL 2 conformance tests

Change-Id: I385f4ce4990597e44ddad4f0fa6db23b661771dc
Reviewed-on: https://chromium-review.googlesource.com/273110Tested-by: Olli Etuaho <oetuaho@nvidia.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Zhenyao Mo <zmo@chromium.org>