[3.6] bpo-31589 : Build PDF using xelatex for better UTF8 support. (GH-3940) (#4683)

Also addresses doc build failures documented in bpo-32200.
(cherry picked from commit 7324b5ce)

Doc/conf.py

@@ -89,11 +89,10 @@ html_split_index = True
 # Options for LaTeX output
 # ------------------------
 
+latex_engine = 'xelatex'
+
 # Get LaTeX to handle Unicode correctly
 latex_elements = {
-    'inputenc': r'\usepackage[utf8x]{inputenc}',
-    'utf8extra': '',
-    'fontenc': r'\usepackage[T1,T2A]{fontenc}',
 }
 
 # Additional stuff for the LaTeX preamble.