http_caldav.c: properly handle all days events with no DTEND (period = 1 day)
configre.in, http_caldav.c, xcal.c: updated to latest RSCALE code in libical
http_caldav.c: if we can't find a cal-home-set for a user, default to remote scheduling
http_caldav.c: removed 1 too many #ifdef HAVE_RSCALE
xcal.c: yet another fix for when libical doesn't have RSCALE support