[O] TeX-master: TeX-master is let-bound

[Christopher Schmidt]

org-export-as-latex (org-latex.el) let-binds TeX-master.  Later on
feature tex may be loaded.  This is a problem, because in that case the
defvar TeX-master of tex (AUCTeX) is ignored.

    Warning: defvar ignored because TeX-master is let-bound

This issue could be fixed by adding (require 'tex nil t).

        Christopher