gpython should treat standard input as a file, not as input to the REPL

This definition works:

class X(object):
def __init__(self, x):
self.x = x
def __str__(self):
return "my name is %s" % self.x

This doesn't:

class X(object):
def __init__(self, x):
self.x = x

def __str__(self):
return "my name is %s" % self.x

Both are accepted by C Python.