tests/gem_render_copy: Add a simple render copy test

The goal is here to both: demonstrate a simple usage of render copy with
the possibility to write pngs to visualize what it's doing and to
provide a test bed to port the render copy function to new
architectures.

Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>

tests/.gitignore

@@ -58,6 +58,7 @@ gem_readwrite
 gem_reg_read
 gem_reloc_overflow
 gem_reloc_vs_gpu
+gem_render_copy
 gem_render_linear_blits
 gem_render_tiled_blits
 gem_ringfill