doc: Update pause documentation and add seealso links between related functions. * input.cc (Finput): Put first sentence description on its own line. Add seealso links. * input.cc (Fyes_or_no):Put first sentence description on its own line. Add seealso links. * input.cc (Fkeyboard): Add seealso link to dbstop. * input.cc (Fkeyboard): Add seealso link to dbstop. * sysdep.cc (Fkbhit): Add seealso link to pause. * sysdep.cc (Fpause): Rewrite docstring. Add seealso links. * sysdep.cc (Fsleep): Add seealso links to usleep, pause. * sysdep.cc (Fusleep): Add seealso links to sleep, pause. * sysdep.cc (Fhave_window_system): Correct bad phrasing in docstring. * listdlg.m: Add seealso link to menu * menu.m: Add seealso link to listdlg.

gnulib-hg = gnulib-hg