Bug#824840: libhunspell api change after upgrade to 1.4

[Jeroen Ooms <jeroen.ooms@stat.ucla.edu>]

Package: libhunspell-dev
Version: 1.4.1

The upgrade of libhunspell-dev to the 1.4 branch changed the API for
get_wordchars_utf16:

  const std::vector<w_char>& get_wordchars_utf16() const;

However 'man 3 husnpell' still lists the old API:

  unsigned short * get_wordchars_utf16(int *" len)

The API change was not advertised elsewhere either. It is not clear if
the change was intended, but it breaks anything that uses this
function.

Upstream issue: https://github.com/hunspell/hunspell/issues/387