base

Fix 2129239: Add an override method for enabling the menu key on signed builds.

There are now 3 ways to enable the menu key:
- by config file (config_disableMenuKeyInLockScreen)
- by 'adb shell setprop ro.monkey=1' (for automated testing on userdebug builds)
- by creating file '/data/local/enable_menu_key (for automated testing on signed user builds)

Security: this only affects the insecure lock screen (not lock pattern) which is generally enabled.