Fix compilation and remove a few more warnings.

* tex.el (TeX-view-program-list-builtin): Fix up paren typo.
* preview.el: Cleanup compiler warnings.  Mark unused arguments.
(error): Don't declare; we don't use it anyway.
(view-exit-action): Declare.
(desktop-buffer-preview): Use normal names for the function's args.
(preview-parse-messages): Remove unused vars `error', `context-start',
and `context' (this last one wasn't even bound).

Signed-off-by: Mosè Giordano <mose@gnu.org>
Move preview changes to ChangeLog-preview.
* latex-test.el: Add proper copyright header.

Signed-off-by: Mosè Giordano <mose@gnu.org>
Add Makefile to run ERT tests.

* tests/latex/latex-test.el (latex): Require latex.el.
(LaTeX-indent-tabular-test/in): Expand file name in load
directory, for automated tests.
(LaTeX-indent-tabular-test/out): Ditto.

* tests/Makefile: New Makefile.

* Makefile.in (.PHONY): Add new check target.
(check): New rule.  Suggest in comments to run it before a new
release.