Document VIS_HTTPSTYLE:

Document VIS_HTTPSTYLE:
VIS_HTTPSTYLE is a new encoding style for use in vis(), strvis() and
  strvisx() that escapes characters according to RFC 1808 (URI encoding).

Since decoding of these require different detection of start-points of
  escaped characters, VIS_HTTPSTYLE can be given as flag to unvis().
  unvis() will then properly decode URIs.

A new function appeared, strunvisx(): strunvisx() behaves similar as
  strunvis(), with one exception: It has an additional flag parameter,
  which is passed to unvis() to archive the effect I described above.