[Orgmode] Use of \w Emacs regexp in org-export-bibtex.el excludes BiBTeX filenames with underscore

[Hsiu-Khuern Tang]

Hi Taru,

In contrib/lisp/org-export-bibtex.el, the BiBTeX file has to match the Emacs
regexp "\w+".  So a line like

#+BIBLIOGRAPHY: mybib_new

will not work because of the underscore character in the filename.  (I suppose
the actual behavior depends on the local Emacs settings that affect the "syntax
table".)  May I propose changing the regexp to "[[:alnum:]_]+"?

Initially, I was stumped by this because I thought \w was a "regular" regexp
:), such as defined in sed, and would match underscores as well.

-- 
Best,
Hsiu-Khuern.