Display signal strength in dBm with visual indicator in the form of a
bar for scan results displayed by wpa_gui-qt4. Any signal > -35dBm is
treated as full signal bar, signals between range of -95<->-35dBm are
displayed linearly. Convert WEXT signal level value to scale that
nl80211 typically reports in dBm. The condition which differentiates
8-bit WEXT dBm and regular dBm is probably fragile, but there is
currently no way to know what the driver is going to report for signal
strength.
Signed-off-by: Kel Modderman <kel@otaku42.de>