Add support for fallback keycodes.

This change enables the framework to synthesize key events to implement
default behavior when an application does not handle a key.
For example, this change enables numeric keypad keys to perform
their associated special function when numlock is off.

The application is informed that it is processing a fallback keypress
so it can choose to ignore it.

Added a new keycode for switching applications.

Added ALT key deadkeys.

New default key mappings:
- ESC -> BACK
- Meta+ESC -> HOME
- Alt+ESC -> MENU
- Meta+Space -> SEARCH
- Meta+Tab -> APP_SWITCH

Fixed some comments.
Fixed some tests.

Change-Id: Id7f3b6645f3a350275e624547822f72652f3defe
diff --git a/include/ui/KeycodeLabels.h b/include/ui/KeycodeLabels.h
index be7db1f..9b1a897 100755
--- a/include/ui/KeycodeLabels.h
+++ b/include/ui/KeycodeLabels.h
@@ -211,6 +211,7 @@
     { "PROG_GREEN", 184 },
     { "PROG_YELLOW", 185 },
     { "PROG_BLUE", 186 },
+    { "APP_SWITCH", 187 },
 
     // NOTE: If you add a new keycode here you must also add it to several other files.
     //       Refer to frameworks/base/core/java/android/view/KeyEvent.java for the full list.