Copy current native event APIs over; start updating
sample code to use them.
The native activity sample is now much more real, creating
its own worker thread, which now monitors and prints any
incoming input events.
Note that due to the lack of default key handling, pressing
back no longer works! Will be fixed in a bit. This code
also needs to be refactored to put the engine part into
a separate source file.
Change-Id: I2ab3e6d9f840b99ec9a05bbc0d2cd9314beb23d7
