efficiency tweaks, and fix a few minor bugs in help_init() where "Up"
and "Space" might not be displayed properly and the help browser
wouldn't work if fewer than 24 columns were available


git-svn-id: svn://svn.savannah.gnu.org/nano/trunk/nano@1885 35c25a1d-7b9e-4130-9fde-d3aeb78583b8