Validator functions implementation

[Andrew Janke]

Hi Octave folks,

Are you interested in having an Octave implementation of the Matlab 
"validator" functions - mustBeNumeric(), mustBeNonempty(), and friends? 
I have a Matlab-based implementation of them that wouldn't be hard to 
port over, maybe in time for Octave 6.

https://github.com/apjanke/matlab-validoozy

Let me know if you're interested, and if so, whether you're interested 
in my extensions (the "label" argument and the additional validators) or 
just base Matlab-compatible implementations.

Cheers,
Andrew