- dictmgr.hxx and dictmgr.cxx files were removed from hunspell
- Some files were complaining about a missing <hunspell/hunspell.h>
  include. Changing it to <hunspell.h> fixed it.

Task-number: QTBUG-57415
Change-Id: Ib2331bf28b3f60370730ca3534469e463d062dee
Reviewed-by: Jarkko Koivikko <jarkko.koivikko@code-q.fi>
Reviewed-by: Mitch Curtis <mitch.curtis@qt.io>