lexical function binding for elisp

lexical function binding for elisp

* module/language/elisp/compile-tree-il.scm (access-variable)
  (reference-variable, set-variable!): Handle globally-bound non-special
  variables.

  (bind-lexically?): Create lexical bindings for flet and flet*.

* module/language/elisp/runtime.scm (reference-variable, set-variable!):
  Handle globally-bound non-special variables.

  (built-in-func): Set the variable directly instead of storing the
  function in a fluid.

* module/language/elisp/runtime/subrs.scm (funcall): Call apply
  directly.

* test-suite/tests/elisp-compiler.test ("Function Definitions")["flet
  and flet*"]:

Signed-off-by: Andy Wingo <wingo@pobox.com>