Added implementation for querying
GL_FRAMEBUFFER_ATTACHMENT_TEXTURE_LAYER in
GetFramebufferAttachmentParameteriv.

Change-Id: Ib25ba51bf68c9d979f80cc65ba7059366b5f1ae4
Reviewed-on: https://swiftshader-review.googlesource.com/3541Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>