BUG: Allos linalg.solve to handle zero equations.

This was previously correct, but the special case was missing
since the gufunc code cannot handle it.
Merge pull request #3848 from seberg/solve_0k

BUG: Allos linalg.solve to handle zero equations.
BUG: preserve ndarray subclasses in median

closes gh-3846
Merge pull request #3851 from juliantaylor/median-subclass

BUG: preserve ndarray subclasses in median