Merge branch 'next'

* next:
  minor, lose local copy of p/ep pair in fixc_render_fixml_rndr() and use ctx.{p,ep} instead
  fix, PEBKAC^2, explicitly mention newlines in reference string literal
  minor, widen the initial buffer size in fixc_render_fixml_rndr() so that an empty Batch message would fit
  fix, PEBKAC, provide proper result to compare fixml documents to, ...
  minor, turn off downsizing of rndr buffers, instead pass on alloc size in slot z
  fix, PEBKAC, upon mremap() in resz_rndr() make sure the buffer size will be adapted
  test, add regressions for Batch only empty message rendering
  minor, prefer mmap based memory allocation all the way through
  Revert "minor, make fixc_rndr_s str slot const to indicate that it's fixc's responsibility"
  minor, make fixc_rndr_s str slot const to indicate that it's fixc's responsibility
  minor, allow stack in fixc_fixup() to grow (and shrink)
  test, add regression that is a problem for um-apfd