Sprint smoothing + Ironsights fix

When crouched and moving, using ironsights would roll you. Sprint and
walk still do. Need to stop them from continuing to roll you despite no
longer pressing sprint/walk key for as long as you are holding
+movedown.

Sprint smoothing just adds a delay to the check for ground, causes
slight delay when running off a ledge before sprint stops but it's
barely noticeable, in fact I think it looks better.