Added mesh transform test

Tests/test_image_transform.py

@@ -2,4 +2,15 @@ from tester import *
 
 from PIL import Image
 
-success()
+def test_quad():
+    # one simple quad transform, equivalent to scale & crop upper left quad
+    im = lena('RGB')
+    (w,h) = im.size
+    transformed = im.transform(im.size, Image.QUAD,
+                               (0,0,0,h/2,
+                                w/2,h/2,w/2,0), # ul -> ccw around quad
+                               Image.BILINEAR)
+    
+    scaled = im.resize((w*2, h*2), Image.BILINEAR).crop((0,0,w,h))
+    
+    assert_image_equal(transformed, scaled, 10)