InCallUI: Enable Speaker on Proximity (3/3)

PS2: Recommendation From Peter Gregus
	on fetching proximity values
PS3: Ensure listener is destroyed
	&& attempt to fix issues with
	headsets still allowing the
	setting to activate...
===
restoring abandoned commit from:
https://gerrit.slimroms.net/#/c/15839/
PS: Fix logic

Change-Id: I2f0aab1dc66ed8297249e0858207ddaf63ef0d35

Conflicts:
	src/com/android/incallui/ProximitySensor.java