This is necessary for cube or 2D array shadow texture sampling
functions which need the fourth texture coordinate component for
depth comparison while also taking a lod or bias parameter.

Change-Id: I1e1399f134e22cecaff97a224df2c13c57ba3a40
Reviewed-on: https://swiftshader-review.googlesource.com/13551Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>
Tested-by: Nicolas Capens <nicolascapens@google.com>