Inconsistent function names for getting global pointers.

[janEntikan]

ButtonRegistry, Notify and TypeRegistry use ptr() as function name and ClockObject has get_global_clock. Most classes that use a global pointer tend to go with the get_global_pointer function name, which is arguably not a very good name either but it's what I'm used to by now.

As a side note, ptr() is a nim builtin, making parsing that one more peculiar.