[Beignet] Copyright problems in test suite

[Rebecca N. Palmer]

The Beignet test suite contains two groups of files that do not appear 
consistent with the project's LGPL license:

1. Derived from the Len(n)a standard test image: 
kernels/lenna128x128.bmp kernels/compiler_box_blur_float_ref.bmp 
kernels/compiler_box_blur_ref.bmp
This is not generally distributable (https://bugs.debian.org/758442), 
and can simply be replaced by an arbitrary input image and its 
corresponding expected outputs.

2. Derived from Shadertoy shaders (stated in 
utests/compiler_shader_toy.cpp):
kernels/compiler_chocolux.cl kernels/compiler_chocolux_ref.bmp 
kernels/compiler_clod.cl kernels/compiler_clod_function_call.cl 
kernels/compiler_clod_ref.bmp kernels/compiler_julia.cl 
kernels/compiler_julia_function_call.cl 
kernels/compiler_julia_no_break.cl 
kernels/compiler_julia_no_break_ref.bmp kernels/compiler_julia_ref.bmp 
kernels/compiler_mandelbrot.cl kernels/compiler_mandelbrot_alternate.cl 
kernels/compiler_mandelbrot_alternate_ref.bmp 
kernels/compiler_mandelbrot_ref.bmp kernels/compiler_menger_sponge.cl 
kernels/compiler_menger_sponge_no_shadow.cl 
kernels/compiler_menger_sponge_no_shadow_ref.bmp 
kernels/compiler_menger_sponge_ref.bmp kernels/compiler_nautilus.cl 
kernels/compiler_nautilus_ref.bmp kernels/compiler_ribbon.cl 
kernels/compiler_ribbon_ref.bmp
These particular shaders are no longer on Shadertoy, but the default 
license there is CC-BY-NC-SA (https://www.shadertoy.com/terms).  What 
license are these under?
As these are tests, they can be removed if necessary.