Some touchscreens seem to oscillate heavily for a while after touching
the screen.  Implement support for sampling the screen until we get two
consecutive values that are close enough.
Signed-off-by: NImre Deak <imre.deak@nokia.com>
Signed-off-by: NJuha Yrjola <juha.yrjola@nokia.com>
Signed-off-by: NDavid Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: NDmitry Torokhov <dtor@mail.ru>