Onwards to lexical binding (attempt 1)

[Tassilo Horn]

Hi all,

on the new branch lexical-binding-attempt-1, I've squashed all
"reference to free variable" warnings in latex.el and context.el by
declaring them properly with defvars and with a prefix, and changing all
users.

This affects in latex.el

  LaTeX-done-mark
  LaTeX-level
  LaTeX-name
  LaTeX-title
  LaTeX-toc

and in context.el

  ConTeXt-done-mark
  ConTeXt-level
  ConTeXt-name
  ConTeXt-title
  ConTeXt-reference

which were previously neither prefixed nor declared.

Of course, that is an incompatible change which will break user
LaTeX-section-hook functions which accessed those unprefixed variables.
But if we want to go lexical-binding (which I think we should), there's
no way around that.

Of course, I did not test too much (and ConTeXt not at all), so it would
be great if you could give it a whirl.  There are chances that I might
have changed an occurrence which I shouldn't have.

We still have such issues in tex.el with the variable `file' and some
others.  If someone wants to take care of that in a similar vein, feel
free to give it a shot.

Bye,
Tassilo