bug#19665: 25.0.50; python.el: mark defun bug when point is in class statement

[Carlos Pita <carlosjosepita@gmail.com>]

Specifically, try the example below:

```
class A: pass


class B:

    def __init__(self): pass

    def fun(self): pass

class C: pass
```

1) If point is in the line immediately after "class B:", then C-M-h will
select the entire class B definition, as expected.

2) If point is in the line "class B:", then C-M-h will select just the
definition of the fun method, which is entirely unexpected!

Cheers
--
Carlos