Issue #6181: Fixed errors in tkinter.Listbox docstrings.

Based on patch by Guilherme Polo.

Lib/tkinter/__init__.py

@@ -2597,10 +2597,10 @@ class Listbox(Widget, XView, YView):
         return self.tk.splitlist(self.tk.call(
             self._w, 'curselection'))
     def delete(self, first, last=None):
-        """Delete items from FIRST to LAST (not included)."""
+        """Delete items from FIRST to LAST (included)."""
         self.tk.call(self._w, 'delete', first, last)
     def get(self, first, last=None):
-        """Get list of items from FIRST to LAST (not included)."""
+        """Get list of items from FIRST to LAST (included)."""
         if last:
             return self.tk.splitlist(self.tk.call(
                 self._w, 'get', first, last))
@@ -2634,7 +2634,7 @@ class Listbox(Widget, XView, YView):
         self.tk.call(self._w, 'selection', 'anchor', index)
     select_anchor = selection_anchor
     def selection_clear(self, first, last=None):
-        """Clear the selection from FIRST to LAST (not included)."""
+        """Clear the selection from FIRST to LAST (included)."""
         self.tk.call(self._w,
                  'selection', 'clear', first, last)
     select_clear = selection_clear
@@ -2644,7 +2644,7 @@ class Listbox(Widget, XView, YView):
             self._w, 'selection', 'includes', index))
     select_includes = selection_includes
     def selection_set(self, first, last=None):
-        """Set the selection from FIRST to LAST (not included) without
+        """Set the selection from FIRST to LAST (included) without
         changing the currently selected elements."""
         self.tk.call(self._w, 'selection', 'set', first, last)
     select_set = selection_set