Merge pull request RustPython#1061 from RustPython/xdrlib

Add endianness support to struct module.

Author: windelbouwman

tests/snippets/test_struct.py

@@ -8,3 +8,17 @@
 assert v1 == 14
 assert v2 == 12
 
+data = struct.pack('<IH', 14, 12)
+assert data == bytes([14, 0, 0, 0, 12, 0])
+
+v1, v2 = struct.unpack('<IH', data)
+assert v1 == 14
+assert v2 == 12
+
+data = struct.pack('>IH', 14, 12)
+assert data == bytes([0, 0, 0, 14, 0, 12])
+
+v1, v2 = struct.unpack('>IH', data)
+assert v1 == 14
+assert v2 == 12
+