Python 2's PyNumberMethods has nb_inplace_divide, but Python 3 does
not. This patch adds it for Python 2.
This buglet didn't cause much fallout because the only non-NULL entry
in value_object_as_number after this is for valpy_divide; and the
missing slot caused it to slide up to nb_floor_divide (where
nb_true_divide was intended).
2016-05-24 Tom Tromey <tom@tromey.com>
* python/py-value.c (value_object_as_number): Add
nb_inplace_divide for Python 2.