[Patch] add Menu::clear()

[Abdelrazak Younes]

Lars,

qt4 frontend needs a Menu::clear() method to compile. Could you apply 
this please?

Thanks in advance,
Abdel.
Index: D:/msys/home/yns/src/lyx-svn/trunk/src/MenuBackend.h
===================================================================
--- D:/msys/home/yns/src/lyx-svn/trunk/src/MenuBackend.h        (revision 13299)
+++ D:/msys/home/yns/src/lyx-svn/trunk/src/MenuBackend.h        (working copy)
@@ -155,6 +155,8 @@
        bool empty() const { return items_.empty(); }
        ///
        ItemList::size_type size() const { return items_.size(); }
+       /// Clear the Menu Content.
+       void clear() { items_.clear(); }
        ///
        MenuItem const & operator[](size_type) const;
        ///