FROMLIST: anv: Add support for the variablePointers feature

Not to be confused with variablePointersStorageBuffer which is the
subset of VK_KHR_variable_pointers required to enable the extension.
This means we now have "full" support for variable pointers.

Archived-At: https://lists.freedesktop.org/archives/mesa-dev/2017-October/173537.html
(am from https://patchwork.freedesktop.org/patch/183830/)

BUG=b:68708929
TEST=TODO

Change-Id: I9557bd8f72ce6a554b28d068e06f4867fe83be10
2 files changed