[lazarus] Attach menu to window

[Micha Nelissen]

Hi,

Currently the menu is immediately attached to a window upon creation. 
However, when creating all the entries this causes an huge delay, 
because the window gets redrawn for every menu item change and add.

Therefore I suggest introducing an LM_ATTACHMENUTOWINDOW or something 
alike. Then all menu items are created first and when all is done a 
message sent attaching the menu causing a redraw only once. The message 
could be sent from TCustomForm.CreateWnd after FMenu.HandleNeeded for 
example.

Please, someone from the GTK team respond for comments :).

Regards,

Micha.