Patrick Storz authored Sep 13, 2018 and LRN committed Sep 18, 2018

Commit 359df028 changed the
code to send GDK_SCROLL_SMOOTH with deltas instead of
GDK_SCROLL_(UP|DOWN|LEFT|RIGHT).

Windows defines deltas inversed for vertical direction
(positive values mean the wheel was turned forward)
but not for horizontal direction
(positive values mean the wheel was turned towards the right).

This commit fixes behavior as both axes were inverted previously.