Moved decorator_c into namespace decoders.
Moved event-handler-decorator into event-handlers dir.
Moved event_handler_decorator_c into event_handlers namespace.
Event handler decorators now wrap refs rather than shared_ptrs.
Added alt modifier event handler decorator, unit tests.
Event handler decorator now decorates event_handler_{c,i}.
Alt modifier decorator now decorates event_handler_{c,i}.
Added alt prefix decoder.
Added lib/src/terminal-lib-priv.cpp.

Updated paths to include src/.
Moved what could be from inc to src.