Add allocators for controls & menus

[ProgramMax]

Is your feature request related to a problem? Please describe.
maxGUI maintains lifetimes of controls and menus. Just like it maintains lifetimes of forms.
For forms, a form allocator is provided. This allows users to provide their own allocator to be used inside maxGUI.
Controls and menus need this same thing.

Describe the solution you'd like
A control / menu allocator.

Describe alternatives you've considered
Always using 'new', as currently happens. This works for probably 99% of use cases. And thus it should be the easy default. But ultimately, there should be an option.