structured arrays with different byteorders do not compare

Equality comparisons don't work on structured arrays if they have different byteorders.  This seems to be inconsistent with what happens with non-structured arrays.  Should this be considered a bug?  If so, I'd be happy to take a crack at fixing it.

```
In [1]: import numpy as np

In [2]: x = np.array([5], dtype=">i8")

In [3]: y = np.array([5], dtype="<i8")

In [4]: x == y
Out[4]: array([ True], dtype=bool)

In [6]: x = np.array([(5,)], dtype=[('a', '>i8')])

In [7]: y = np.array([(5,)], dtype=[('a', '<i8')])

In [8]: x == y
Out[8]: False
```