Add testcase for #664

tests/run/starred_target_T664.pyx

+def assign():
+    """
+    >>> assign()
+    (1, [2, 3, 4, 5])
+    """
+    a, *b = 1, 2, 3, 4, 5
+    return a, b
+
+def assign3():
+    """
+    >>> assign3()
+    (1, [2, 3, 4, 5], 6)
+    """
+    a, *b, c = 1, 2, 3, 4, 5, 6
+    return a, b, c
+
+def assign4():
+    """
+    >>> assign4()
+    (1, [2, 3, 4], 5, 6)
+    """
+    a, *b, c, d = 1, 2, 3, 4, 5, 6
+    return a, b, c, d