Weak symbols

[gedankenexperimenter]

I think it will work to use weak symbols for the master hook function definitions in the core, and make parts of the HID module(s) selectively link that way. I need to test this.

[gedankenexperimenter]

I want everything that's pluggable/selectable to be defined somewhere in the sketch, with preprocessor macros or by other means.

Plugin hook functions could be done with weak symbols, maybe, in order to bring them in without reading config files in the plugin repo.

HID endpoints (i.e. BootKeyboard) could have the static objects defined only inside weak wrapper functions (in core?), and if those functions are overridden elsewhere, they should be dropped from the program. Test this.