bug#30048: 27.0.50; bibtex-reference-keys is in reverse order

[Basil L. Contovounesios]

The function bibtex-parse-keys in lisp/textmodes/bibtex.el accumulates
BibTeX reference keys in the reverse order of that in which they appear
in the corresponding buffer, before storing them in the variable
bibtex-reference-keys.  AFAICT, there is no utility or need for this
ordering, which can be a nuisance for programs wishing to make in/direct
use of this variable.  See bug#28998 for more concrete justification.

A patch to reverse the accumulated value of bibtex-reference-keys
follows in my next email.

Thanks,

-- 
Basil

In GNU Emacs 27.0.50 (build 13, x86_64-pc-linux-gnu, X toolkit, Xaw3d scroll 
bars)
 of 2018-01-03 built on thunk
Repository revision: f8b4e87d5d4f57954b50677add76ce5136211dc1
Windowing system distributor 'The X.Org Foundation', version 11.0.11905000
System Description: Debian GNU/Linux testing (buster)