Add support for auto-orientable toolbars to AUI.

Allow wxAUI to change the toolbar orientation depending on where is it docked.
It is also now possible to specify wxAUI_TB_VERTICAL or HORIZONTAL to force
the toolbar to be always oriented in the given sense and to prevent it from
being docked at the sides incompatible with it.

Closes #11712.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@65061 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

docs/changes.txt

@@ -408,6 +408,11 @@ MSW:
 - Fix Cygwin 1.7 build (David Gangola).
 - Allow using wxDC::DrawText() with multiline texts.
 
+All (GUI):
+
+- wxAUI: support auto-orientable toolbars (wsu).
+
+
 2.9.1:
 ------