Build clean up, etc. from Sebastian

Build clean up, etc. from Sebastian

* merges:
  Summary: cosmetics, conditionalise seemingly unused vars in movemail.c Keywords: refactor warn-fix
  Summary: cosmetics, refactor large parts of make-docfile.c Keywords: refactor warn-fix
  Summary: fix, -Winline -> only if maximum warning output Keywords: bldchn code hygiene warn-fix
  Summary: fix, unused warnings in gnuserv.c Keywords: bldchn code hygiene warn-fix
  Summary: fix, signedness and unused warnings in gnuserv et al. Keywords: bldchn code hygiene warn-fix
  Summary: fix, clean up signedness problem in gnuserv and friends Keywords: bldchn code hygiene warn-fix
  Summary: cosmetics, declare yow internal functions static Keywords: bldchn
  Summary: cosmetics, fix some signedness and shadow warnings in gnuclient Keywords: bldchn
  Summary: cosmetics, fix some warnings about signedness Keywords: bldchn
  Summary: chore, deactivate some warnings again (if not aggressive) Keywords: bldchn