Fixed `TouchBegan` reporting wrong coordinates

* So far `sf::Event::TouchBegan` always reported the coordinates of the
first pointer/finger.

I've provided an updated example app with commit 5e14bc03bad347c932e3adca62a38a359b0fe76a.

* Touch the screen to create expanding circles/ripples.
* To reproduce the bug, touch the screen at one position and keep your finger on the screen.
* Tap a second or third time.
* All additional circles will originate at the position of your first finger press rather than the new touch locations.