test: Add a blur test case

Derived from pixman-rotate.c test case.

Signed-off-by: Bryce Harrington <b.harrington@samsung.com>
(squash) Enable test to actually run

Signed-off-by: Bryce Harrington <b.harrington@samsung.com>
(squash) Trim out bits particular to downscaling test

Signed-off-by: Bryce Harrington <b.harrington@samsung.com>
test: Add shadow functionality to blur test case

Signed-off-by: Bryce Harrington <b.harrington@samsung.com>
test: Draw a ring to test blur rendering

Design lifted from Henry Song's cairo-glx-shadow-ring.c example.
test: Use current output as reference image for blur
shadow: release shadow cache before set device status to FINISHED
gl/msaa: check framebuffer status for msaa framebuffer