Merge branch 'next'

* next:
  fix, make output format buffer size slightly larger (4 times the previous size)
  test, provide regressions for short buffer bug
  fix, PEBKAC, don't pass uninitialised args to dt_strfdt()
  minor, extend dt_strfdt() to take a zdiff parameter, ...
  minor, use pointers in dtz_forgetz() and dtz_enrichz() and return the difference applied
  minor, refactor dtz_enrichz() and dtz_forgetz() to use dt_dtadd() for the core work (addition of zdiff)
  fix, allow demotion of zone-specified files into UTC with flag `znfxd'
  test, PEBKAC, reflect reality with new multi-sed regressions
  minor, actually fix up the zone diff in strpdt parsers yielding UTC time stamps all the time
  fix, PEBKAC, only try to parse zone diff specs in dt mode
  fix, PEBKAC, always return a proper result in try_zone()
  minor, introduce %Z zone difference specifier
  minor, introduce %Z zone difference specifier
  cosmetics, don't leave #if-0'd code in headers
  fix, make GPERF var default to gperf
  chore, list fmt-special as EXTRA_ltrcc_SOURCE
  minor, support reading zone differences in std parser
  test, provide regression tests for dconv's multiple occurrence sedding
  minor, backport new test suite file naming and flow policies to example generators (gentexi, genh2m)