Removed compilation warning generating always true comparison.

Signed-off-by: Timo J. Rinne <tri@iki.fi>
Elaborated the warning removal and made it still explicitly
check that the escape key character is less than 128.

Signed-off-by: Timo J. Rinne <tri@iki.fi>
Invalid escape key defaults to Ctrl-^ but empty escape
key causes there being no escape key at all.

Signed-off-by: Timo J. Rinne <tri@iki.fi>
Set escape pass key correctly in default case.

Signed-off-by: Timo J. Rinne <tri@iki.fi>