> From: Philipp Stephani <p.stephani2@gmail.com>
> Date: Thu, 05 Jan 2017 14:46:01 +0100
>
> (string-match-p "[[:blank:]]" "\N{HAIR SPACE}")
> => nil, expected 0
>
> [[:blank:]] should be the same as \h in PRCE.

We are consistent with our documentation, but I agree that it would be
good to extend [:blank:], as proposed here:

  http://www.unicode.org/reports/tr18/tr18-19.html#Compatibility_Properties

Patches to that effect are welcome.