nconf: function keys line, change background color for better readability

•  In function keys line descriptions black on darkblue are almost
   impossible to read.  Change colors to black on brown.

Signed-off-by: Roland Eggner <edvx1@systemanalysen.net>
Tested-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>