* Update helpcontent2 from branch 'master'
  - Mention ICU list of regular expressions
    
    ... because we use that engine under the hood.
    
    Change-Id: Icf72dfe7534ccad26cc4ee0aefd7d3f03817e65d
    Reviewed-on: https://gerrit.libreoffice.org/58969
    Tested-by: Jenkins
Reviewed-by: Olivier Hallot <olivier.hallot@libreoffice.org>