Merge branch 'next'

* next:
  chore, move auxiliary build stuff into build-aux
  chore, never prepend a dash to final filename in explode-by-* mode, ...
  chore, be clear about that --explode-by-* options are mutually exclusive
  minor, don't prepend dashes if --outfile|--into is a directory in ute-slab
  minor, don't open internal outfn for neither explode-by-interval nor explode-by-symbol
  minor, provide prefixes both for explode-by-interval as well as explode-by-symbol
  fix, PEBKAC, reset the stamp for each call to info1()