ox-latex.el: fix interpretation of org-latex-pdf-process

* ox-latex.el (org-latex-export-to-pdf):  The documentation for
`org-latex-pdf-process' states that "%bib" will be expanded into the
current binding of `org-latex-bibtex-compiler'.  However, the
`org-latex-export-to-pdf', where the expansion takes place, expects
"%bibtex" instead.  This fix will accept "%bib" as well as "%bibtex"
as markers for `org-latex-bib-compiler'.

This fixes a regression from f6187deca (ox-latex: Small refactor,
2015-09-13).

TINYCHANGE

lisp/ox-latex.el

@@ -3660,12 +3660,12 @@ produced."
 		     (match-string 0)))
 	      "pdflatex"))
 	 (process (if (functionp org-latex-pdf-process) org-latex-pdf-process
-		    ;; Replace "%latex" and "%bibtex" with,
-		    ;; respectively, "%L" and "%B" so as to adhere to
-		    ;; `format-spec' specifications.
+		    ;; Replace "%latex" with "%L" and "%bib" and
+		    ;; "%bibtex" with "%B" to adhere to `format-spec'
+		    ;; specifications.
 		    (mapcar (lambda (command)
 			      (replace-regexp-in-string
-			       "%\\(?:bib\\|la\\)tex\\>"
+                               "%\\(?:\\(?:bib\\|la\\)tex\\|bib\\)\\>"
 			       (lambda (m) (upcase (substring m 0 2)))
 			       command))
 			    org-latex-pdf-process)))