- Add in Pico's -p flag, (-p, --preserve). To preserve the XON and XOFF...

    - Add in Pico's -p flag, (-p, --preserve).  To preserve the XON and XOFF keys (^Q and ^S).  Add warning if we invoke -p and add checks for using --preserve (to skip warning) and --pico (to force showing it).  New flag PRESERVE, function do_preserve_msg(), changes to main(), signal_init()

git-svn-id: svn://svn.savannah.gnu.org/nano/trunk/nano@1340 35c25a1d-7b9e-4130-9fde-d3aeb78583b8