user32/tests: Test MDI menu updating when window titles are changed.
user32: Always refresh the MDI menu on WM_MDISETMENU. Even if there was not a previous menu.
user32: Refresh MDI menus when DefMDIChildProc(WM_SETTEXT) is called. Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=21855