function binding fixes

function binding fixes

* module/language/elisp/bindings.scm (bindings): Add `function-bindings'
  field.
  (make-bindings): Initialize the `function-bindings' field.
  (get-function-binding, with-function-bindings): New functions.

  (access-variable, reference-variable, set-variable!): Remove the
  `module' argument and only handle references to the value cell. All
  callers changed. Callers passing `function-slot' as the module changed
  to use the corresponding functions for the function cell instead.

  (access-function, reference-function, set-function!): New procedures.

  (compile-flet, compile-labels): Use `with-function-bindings' instead
  of `with-lexical-bindings'.