Revert "Remove 'Allow custom buttons' checkbox (1/2)" - fix for compiling problems

This reverts commit 97e968c8ec439ba195e5d462ee64f813dcb75e4b.

Conflicts:
	policy/src/com/android/internal/policy/impl/PhoneWindowManager.java

	modified:   core/java/android/provider/Settings.java
	modified:   policy/src/com/android/internal/policy/impl/PhoneWindowManager.java