Revert "remove headset volume warning"

This reverts commit 6e4f854ebcd37f130bdeb5ef6f572465777e65f1.
Merge branch 'cm-11.0' of git://github.com/CyanogenMod/android_frameworks_base into cm-11.0

(cherry picked from commit ddd618fc747cc17f9472ceb73851911066df6802)

Conflicts:
	core/java/android/provider/Settings.java
	packages/SystemUI/src/com/android/systemui/statusbar/phone/PhoneStatusBar.java
	policy/src/com/android/internal/policy/impl/PhoneWindowManager.java