kill app long press back

Conflicts:
	core/res/res/values/symbols.xml
	policy/src/com/android/internal/policy/impl/PhoneWindowManager.java
holdback to kill policy change
Revert "holdback to kill policy change"

This reverts commit cdb7cbfe9f565e0d2352e29da6fedb0df22961a8.
fix a error in back to kill
make back to kill use current policy