Currently OpenCL devices are packing images into a single texture,
which means technically number of textures is not limited here.
Now OpenCL will use same number of textures as CPU. If we want
to bump number of textures further, this values are to be modified
in sync.
NOTE OpenCL still does not support float textures.
Original patch from a guy called bliblubli in the tracker with
some own modifications.
Reviewers: brecht, dingto, sergey
Differential Revision: https://developer.blender.org/D1530
8a1afc28db