Improve man search

Improve the helper script for performing the search on man pages:
- pass the language and the search method (and/or) to it
- use an array to compose the command line of apropos
- pass the language to apropos
- if the search method is "and", pass --and to apropos (its default is
  like "or)
- split the search string by "+"; it is a kludge, but needed due to the
  internal handling of search in khelpcenter currently

BUG: 103265