elisp lambda list parsing

elisp lambda list parsing

* module/language/elisp/compile-tree-il.scm (split-lambda-arguments):
  Remove.

  (parse-lambda-list, make-simple-lambda): New procedures.

  (compile-lambda): Use `parse-lambda-list' and `make-simple-lambda'.
  Set empty rest arguments to the empty list instead of `#nil'.

* test-suite/tests/elisp-compiler.test ("Lambda Expressions")["rest
  argument"]: Use Elisp `null' instead of a Scheme equality check.