Bug? numpy.dtype is not sortable.

[tkf]

I find this when I am writing the pull request #1098. As it is loosely related to the pull request, I am reporting here as a separate issue.

It looks like dtype does not support sorting:

>>> from numpy import dtype
>>> sorted([dtype('bool'), dtype('float64'), dtype('complex64'),
...         dtype('float64'), dtype('object')])
[dtype('bool'),
 dtype('float64'),
 dtype('complex64'),
 dtype('float64'),
 dtype('object')]

core.internals._consolidate relies sortability of dtype. Probably it is better to sort using dtype.name as I did in bae8155?

[tkf]

Fixed by da8bc6c. Thanks for merging it!