Copying a mock object breaks coverage utility about mock HOT 5 CLOSED

This is due to an infinite recursion in Mock.__getattr__.  Add this to the top 
to fix the problem:

    def __getattr__(self, name):
        if name == "_methods":
            raise AttributeError(name)

PS: a longer write-up of the issue: 
http://nedbatchelder.com/blog/201010/surprising_getattr_recursion.html

Fixed, but the test is a bit brutal (call sys.setrecursionlimit(sys.maxint) and 
copying a Mock segfaults without the fix). I did try the sys.settrace trick, 
but for some reason that didn't work (the trace function wasn't removed during 
the test even after the recursion).