* lisp/progmodes/modula2.el: Use SMIE and skeleton.

* lisp/progmodes/modula2.el: Use SMIE and skeleton.
(m2-mode-syntax-table): (*..*) can be nested.
Add //...\n.  Fix paren syntax.
(m2-mode-map): Remove LF and TAB bindings.
(m2-indent): Add safety property.
(m2-smie-grammar): New var.
(m2-smie-refine-colon, m2-smie-refine-of, m2-smie-backward-token)
(m2-smie-forward-token, m2-smie-refine-semi, m2-smie-rules): New funs.
(m2-mode): Use define-derived-mode.
(m2-newline, m2-tab): Remove.
(m2-begin, m2-case, m2-definition, m2-else, m2-for, m2-header)
(m2-if, m2-loop, m2-module, m2-or, m2-procedure, m2-with, m2-record)
(m2-stdio, m2-type, m2-until, m2-var, m2-while, m2-export)
(m2-import): Use define-skeleton.
* test/indent/modula2.mod: New file.