Revert massive replacement of empty list creation sentences. The use of '[list]' instead of '{}' adds semantics that could be used for performance improvements in the future, such as using a different internal representation. There is already work in this direction, avoiding the generation of the string representation during comparison of empty strings (huge thanks to Stefan Sobernig for the pointer: https://core.tcl.tk/tcl/info/44527c632ed609c2).
calendar reform (part 2): - make "forgotten" fields "related_link_url", "related_link_text", "redirect_to_rel_link_p" of acs-events usable from the calendar. - add web interface for "location" field as well - bump version to 2.10.0d4