[O] [patch] Add three "xelatex" config items to "org-latex-to-pdf-process"

[FengShu]

Xelatex should be pdflatex with enhanced font handling capability.
and its fonts configure for Chinese is  much much  more simple than 
pdflatex, for it can use *ttf* *otf* fonts in the system easily.

Add item:
1.  2 runs of xelatex
2.  3 runs of xelatex
3.  xelatex,bibtex,xelatex,xelatex



diff --git a/lisp/org-latex.el b/lisp/org-latex.el
index 6d46501..189e206 100644
--- a/lisp/org-latex.el
+++ b/lisp/org-latex.el
@@ -657,6 +657,18 @@ This function should accept the file name as its single 
argument."
                   "bibtex %b"
                   "pdflatex -interaction nonstopmode -output-directory %o %f"
                   "pdflatex -interaction nonstopmode -output-directory %o %f"))
+         (const :tag "2 runs of xelatex"
+                ("xelatex -interaction nonstopmode -output-directory %o %f"
+                  "xelatex -interaction nonstopmode -output-directory %o %f"))
+         (const :tag "3 runs of xelatex"
+                ("xelatex -interaction nonstopmode -output-directory %o %f"
+                  "xelatex -interaction nonstopmode -output-directory %o %f"
+                  "xelatex -interaction nonstopmode -output-directory %o %f"))
+         (const :tag "xelatex,bibtex,xelatex,xelatex"
+                ("xelatex -interaction nonstopmode -output-directory %o %f"
+                  "bibtex %b"
+                  "xelatex -interaction nonstopmode -output-directory %o %f"
+                  "xelatex -interaction nonstopmode -output-directory %o %f"))
          (const :tag "texi2dvi"
                 ("texi2dvi -p -b -c -V %f"))
          (const :tag "rubber"