Keep shorthand color form the same way as named colors are kept.

[SomMeri]

Keep shorthand color form the same way as named colors are kept. Fixes #2481 - Interpolated selectors and three letters long id selectors.

[seven-phases-max]

See my last remark at #2481. I suspect we also need to rework the code around "Invalid HEX color code" then (I'm not yet sure how exactly though, most likely the check is just to be removed - so that any #* which is not a hexcolor to be parsed as Anonymous).

[lukeapage]

I think this is okay but not a a bugfix for #2481 if that makes sense - @seven-phases-max I think this keeps coming back to my wanting a proper way of writing a selector and not mixing css values and selectors. The main problem with that was last time I brought it up no-one could agree a syntax. I liked $() other people not.

@seven-phases-max do you agree this should go in even though its not a "proper" fix?

[seven-phases-max]

@lukeapage Yes, I'm actually fine with this change (and for my remark I guess I'll just try to submit a separate patch if I have any good idea).

[seven-phases-max]

I just realized that this PR does something more then just "keep shorthand value". Obviously it preserves the original format as a whole (e.g. including lower/uppercase stuff) thus resulting in issues like gruntjs/grunt-contrib-less#295.
It's fine (not really an issue) but should not we backpatch the changlog then to make it more obvious? (I'm not sure if this normal practice).