[dovecot/core] 833fd6: lib: Clarify *_strsplit_spaces() and add unit test

[GitHub]

  Branch: refs/heads/master
  Home:   https://github.com/dovecot/core
  Commit: 833fd67ffe6a1832d72b3d310e07345a42a7b6ab
      https://github.com/dovecot/core/commit/833fd67ffe6a1832d72b3d310e07345a42a7b6ab
  Author: Timo Sirainen <timo.sirainen at dovecot.fi>
  Date:   2017-02-14 (Tue, 14 Feb 2017)

  Changed paths:
    M src/lib/strfuncs.h
    M src/lib/test-strfuncs.c

  Log Message:
  -----------
  lib: Clarify *_strsplit_spaces() and add unit test