py: Add builtin memoryview object (mostly using array code).

tests/basics/memoryview1.py

@@ -0,0 +1,34 @@
+# test memoryview
+
+# test reading from bytes
+b = b'1234'
+m = memoryview(b)
+print(len(m))
+print(m[0], m[1], m[-1])
+print(list(m))
+
+# test writing to bytes
+try:
+    m[0] = 1
+except TypeError:
+    print("TypeError")
+
+# test writing to bytearray
+b = bytearray(b)
+m = memoryview(b)
+m[0] = 1
+print(b)
+print(list(m))
+
+# test slice
+m = memoryview(b'1234')
+print(list(m[1:]))
+print(list(m[1:-1]))
+
+import array
+a = array.array('i', [1, 2, 3, 4])
+m = memoryview(a)
+print(list(m))
+print(list(m[1:-1]))
+m[2] = 6
+print(a)