test: Add a basic line tester

Starting with exercising drawing of a single segment.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

test/basic-copyarea.c

@@ -264,7 +264,8 @@ static void rect_tests(struct test *t, int reps, int sets, enum target target, i
 		test_compare(t,
 			     real.draw, real.format,
 			     ref.draw, ref.format,
-			     0, 0, real.width, real.height);
+			     0, 0, real.width, real.height,
+			     ""
 	}
 
 	printf("passed [%d iterations x %d]\n", reps, sets);