Merge branch 'next'

* next: (25 commits)
  fix, work around gcc deficiencies when handling transparent unions
  minor, adapt echse.c, echs-lisp.c and echs-filter.c to renamings in fltdef.h
  minor, rename fltdef's opener, closer and psetter
  fix, properly free filter definitions upon freeing echs-mod smobs
  minor, use keyword :output to specify output flavour, superseding :use-* bools
  minor, pass on scheme symbols (as STRs) to psetters
  minor, support :use-zone-name and :use-utc-offset keywords to modify output flavour in zoneinfo dso
  minor, allow to use zone names as defined in the zoneinfo file
  minor, pass on scheme booleans as INTs to psetters
  fix, \nul terminate scheme strings when passed to strflt psetter in __load_ass_kv()
  minor, unify plist putting code in echs-lisp
  minor, put all the psetting beef of zoneinfo DSO into echs_stream_pset()
  Revert "minor, call a DSO's make_stream routine with the number of props coming, i.e. 0"
  minor, adapt echse.c and echs-lisp.c to renamings in strdef.h
  minor, rename strdef's opener, closer and psetter
  minor, migrate zoneinfo DSO to getting all the prop args in make_echs_stream() entry point
  minor, extend property sets by a key-val container echs_prop_s
  minor, call a DSO's make_stream routine with the number of props coming, i.e. 0
  chore, mark unused inlines as unused
  minor, actually flip DST state in zoneinfo DSO
  ...