Try and remove some of SMIE's black magic by generalizing some rules.

Try and remove some of SMIE's black magic by generalizing some rules.
* lisp/emacs-lisp/smie.el (smie-default-backward-token)
(smie-default-forward-token): Strip properties.
(smie-next-sexp): Be more careful with associative operators.
(smie-forward-sexp-command): Generalize.
(smie-backward-sexp-command): Simplify.
(smie-closer-alist): New var.
(smie-close-block): New command.
(smie-indent-debug-log): New var.
(smie-indent-offset-rule): Add a few more cases.
(smie-indent-column): New function.
(smie-indent-after-keyword): Use it.
(smie-indent-keyword): Use it.
Fix up the opener code's point position.
(smie-indent-comment): Only applies at BOL.
(smie-indent-debug): New command.