Activate extra and major modes first
This prevents snippets from a parent mode from overriding those of the
major-mode's (or yas--extra-modes). Snippets of ancestor modes may
still override snippets of some other ancestor modes, but hopefully this
won't cause much trouble in practice.
See [1] and subsequent comments.
[1]: https://github.com/capitaomorte/yasnippet/issues/619#issuecomment-
149127150
* yasnippet.el (yas--modes-to-activate): Reverse result, so that parents
of yas--extra-modes and major are later in the list.
* yasnippet-tests.el (loading-with-cyclic-parenthood)
(extra-modes-parenthood): Test it.
Close #626.