Divide functions have ambiguous specification for integer inputs

[honno]

divide() (and __truediv__/__itruediv__) allows x1 and x2 to be integer arrays, but the ouput is specified as a floating array determined by type promotion, which int types can't promote to.

The spec should either clarify behaviour for both mixed int/float array and two int array scenarios, or note they are out-of-scope similiar to pow().

[kgryte]

The spec can be updated with a note similar to pow. Feel free to submit a PR with the proposed changes.