Also reimplement clear() just in case the implementation of QListView changes in the future and does calls to clear() as QTreeView does.
Also reimplement clear() just in case the implementation of QListView changes in the future and does calls to clear() as QTreeView does.

svn path=/trunk/KDE/kdepim/kontact/src/; revision=819141

lefou/kdepim-noakonadi,lefou/kdepim-noakonadi,lefou/kdepim-noakonadi,lefou/kdepim-noakonadi,lefou/kdepim-noakonadi,lefou/kdepim-noakonadi