Support grouping in Tick formatter based on locale.

When formatting and setting useLocale to True, the numbers greater than
1000 are not grouped as specified by the locale. 1000 should be 1,000 in
certain locales. By setting the last argument to locale.format_string
the locale dependent grouping is honored.

Author: z0rgy

lib/matplotlib/ticker.py

@@ -612,7 +612,7 @@ def _format_maybe_minus_and_locale(self, fmt, arg):
         """
         Format *arg* with *fmt*, applying unicode minus and locale if desired.
         """
-        return self.fix_minus(locale.format_string(fmt, (arg,))
+        return self.fix_minus(locale.format_string(fmt, (arg,), True)
                               if self._useLocale else fmt % arg)
 
     def get_useMathText(self):