Ensure the ShortcutManager uses the correct key character map.

The ShortcutManager used to only receive the key code of the key event
that triggered the shortcut.  This change now provides the shortcut
manager with the whole key event so it can look up the associated
character using the correct key character map.

To make this more efficient, added a mechanism for recycling
key events.  At the moment it is only used by key events owned by the
system process, since clients of the existing API (such as Views)
might continue to hold on to key events after dispatch has finished so
they would break if the key event were recycled by the framework.

Deprecated KeyCharacterMap.BUILT_IN_KEYBOARD.

Change-Id: I4313725dd63f2be01c350c005a41c7fde9bc67e8