Add SMIE support.
* .bzrignore: New file.
* makefile.pkg (test): Use sml-mode-startup.
* sml-mode.el (sml-use-smie): New config var.
(sml-smie-grammar, sml-indent-separator-outdent): New vars.
(sml-smie-rules, sml-smie-definitional-equal-p)
(sml-smie-non-nested-of-p, sml-smie-datatype-|-p)
(sml-smie-forward-token-1, sml-smie-forward-token)
(sml-smie-backward-token-1, sml-smie-backward-token): New functions.
(sml-mode): Don't set forward-sexp-function.
(sml-mode-variables): Set it here instead, and setup SMIE instead
if applicable.