Merge branch 'next'

* next:
  minor, provide uk holidays DSO for proof-of-concept purposes re echs builders
  minor, fix __wday_before() filter, echs_instant_fixup() cannot be used
  hygiene, put default's in all switches in builders.c
  minor, provide control function (shallow though) with CLONE and UNCLONE for mux streams
  minor, use echs_rename() and echs_select() in its multi-variant for de holiday list
  minor, provide control funs for echs_select() and echs_rename() streams
  minor, provide rename builder to rename state names on the fly
  minor, allow multiple selectors in echs_select()