Add the icon-size to the toolbar menu

Add the icon-size to the toolbar menu

- Adds LFUNs for setting the icon size
- Adds icons sizes to the Toolbars menu
- Uses the Toolbars menu as application context menu
- The context menu can now be user defined in stdcontext.inc

When the logical sizes differ and the icon set is changed, the correct
sizes are established only after a restart.

Fixes ticket #10428.

(cherry picked from commit e91572a00bd61d56b5386519b52d316a32974497)
(cherry picked from commit 6c92075799ae8d83f4f38e3c169c40da215e03f2)
(cherry picked from commit 7971dc83efd2a3a2d282af17cded54698340e176)