ox-latex.el: Support for pgf files

* ox-latex.el (org-latex--inline-image): pgf is recognized as an
inline image and treated the same way tikz files.

Python matplotlib and pgfprint for Octave generates pgf plots
rather than TiKZ plots.  They need just be included via \input{.}.

TINYCHANGE

lisp/ox-latex.el

@@ -420,7 +420,7 @@ environment."
   :type 'string)
 
 (defcustom org-latex-inline-image-rules
-  '(("file" . "\\.\\(pdf\\|jpeg\\|jpg\\|png\\|ps\\|eps\\|tikz\\)\\'"))
+  '(("file" . "\\.\\(pdf\\|jpeg\\|jpg\\|png\\|ps\\|eps\\|tikz\\|pgf\\)\\'"))
   "Rules characterizing image files that can be inlined into LaTeX.
 
 A rule consists in an association whose key is the type of link
@@ -1739,7 +1739,7 @@ used as a communication channel."
 		    (if (not (string-match "\\`\\[\\(.*\\)\\]\\'" opt)) opt
 		      (match-string 1 opt))))
 	 image-code)
-    (if (equal filetype "tikz")
+    (if (member filetype '("tikz" "pgf"))
 	;; For tikz images:
 	;; - use \input to read in image file.
 	;; - if options are present, wrap in a tikzpicture environment.