Added detection of touch devices before first touch events happen on Android.

On Android available touch devices are now added with video initialization (like
the keyboard). This fixes SDL_GetNumTouchDevices() returning 0 before any touch
events happened although there is a touch screen available. The adding of touch
devices after a touch event was received is still active to allow connecting
devices later (if this is possible) and to provide a fallback if the new init
did not work somehow. For the implementation JNI was used and API level 9 is
required. There seems to be nothing in the Android NDK's input header (input.h)
to implement everything on C side without communication with Java side.
Fixed bug 2132 - Tests may use invalid SDL_window pointers when windows are closed

norfanin

Some of the tests keep using the pointers of a destroyed SDL_Window when the common event handling handled the close event. The event handler itself does not NULL the pointer after the destruction.

The attached patch adds a loop in the handler that will assign NULL to the destroyed window. It also adds checks to some of the tests so they skip those windows by checking for NULL.