fix crashes on type casts

Cython/Compiler/ExprNodes.py

@@ -3585,7 +3585,7 @@ def unop_node(pos, operator, operand):
         operand = operand)
 
 
-class TypecastNode(ExprNode):
+class TypecastNode(NewTempExprNode):
     #  C type cast
     #
     #  operand      ExprNode

tests/run/r_typecast.pyx

+u"""
+>>> call_method( ExtType() ).method()
+1
+"""
+
+cdef class ExtType:
+    cdef c_method(self):
+        return self
+
+    def method(self):
+        return 1
+
+def call_method(ExtType et):
+    return <ExtType>et.c_method()