Fixes for signal strength

Change-Id: I9c3caf50506f5b02f80f2fd0484d4e1f7c4df940

Conflicts:
	src/drivers/driver_wext.c
Fix mistake

Change-Id: Ia7a64d91e6e6075da765bf5d40931625393915c7
Add combo scan

Change-Id: Idd7c9fad10594da0ab21c51127cca271f27d3108

Conflicts:
	src/drivers/android_drv.h
	src/drivers/driver_wext.c
Add support for disable combo scan for wireless extension

If the combo scan isn't supported by wi-fi firmware, define this:

BoardConfig:
BOARD_WEXT_NO_COMBO_SCAN := true

Change-Id: Id06e097cbe500357c1ddec0a31ca8465822c4533

Conflicts:
	src/drivers/driver_wext.c
	wpa_supplicant/Android.mk