Move some commented-out in-REPL debug code into eastwood.util

from an obscure testcases.f06 namespace.
Add option to print warnings in :emacs-compilation-mode-buffer format

Makes it much easier to step through a file containing many warnings
in Emacs, jumping quickly to the file:line:col of each warning for
you.
Add first version of :unused-locals linter

Has some undesirable warnings remaining described in
changes-detailed.md, but hopefully I can figure out how to eliminate
some of those soon.
Add :unused-locals linter to changes.md
Eliminate a case of undesired :unused-locals warnings