I was really confused about whether strdupW or wcsdup is preferred in shell32. Since strdupW is deprecated, let's just get rid of it so that no one else has to wonder.
-- v2: shell32: Remove unused function strdupW. shell32: Don't use strdupW or heap_* functions in shelllink.c. shell32: Don't use strdupW or heap_* functions in shelldispatch.c. shell32: Don't use strdupW or heap_* functions in shellole.c.