do not redefine `Event.pointerId` on platforms supporting `PointerEvent`
do not redefine `Event.pointerId` on platforms supporting `PointerEvent`

In case of PointerEvent implementation, and with one event fired at a
time, the property will be (already) defined anyway.

rlugojr/melonJS,gopalindians/melonJS,MarkoIvanetic/melonJS,srbala/melonJS,srbala/melonJS,Smoss/Enoru-eco,TukekeSoft/melonJS,melonjs/melonJS,Smoss/Enoru-eco,MarkoIvanetic/melonJS,TukekeSoft/melonJS,rlugojr/melonJS,rlugojr/melonJS,srbala/melonJS,TukekeSoft/melonJS,gopalindians/melonJS,gopalindians/melonJS,melonjs/melonJS