bug#24960: 25.1; etags incorrectly indexes quoted Erlang atoms

There is an error in how etags treats quoted function and record names
in Erlang sources. etags treats the quotes a part of the name, which is
incorrect and prevents xref-find-definitions from working.

In Erlang, the names of functions and records are "atoms". Here's a
description of an atom, from "Erlang Handbook"
(http://opensource.erlang-solutions.com/erlang-handbook/):

> An atom is a symbolic name, also known as a literal. Atoms begin with
> a lower-case letter, and may contain alphanumeric characters,
> underscores (_) or at-signs (@). Alternatively atoms can be specified
> by enclosing them in single quotes ('), necessary when they start with
> an uppercase character or contain characters other than underscores
> and at-signs.

Note that the quotes around quoted atoms are not part of the name. That
is, the following two strings represent the same atom: xyzzy 'xyzzy'
Because etags currently treats the quotes as part of the name, an
attempt to look up the name using the unquoted form will fail. I have
created a patch to fix this bug.

Attached is the patch (etags.patch), an example Erlang source file that
demonstrates the bug (test.erl), a TAGS file generated from the current
etags program (TAGS), and a TAGS file generated from the patched etags
program (TAGS.new).
--

David Hull

In GNU Emacs 25.1.1 (x86_64-apple-darwin13.4.0, NS appkit-1265.21 Version 10.9.5 (Build 13F1911))
of 2016-09-20 built on builder10-9.porkrind.org
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From:	David Hull
Subject:	bug#24960: 25.1; etags incorrectly indexes quoted Erlang atoms
Date:	Thu, 17 Nov 2016 17:52:43 -0800