[src/misc.c] Fixes of mc_wheel_scroll().
[src/misc.c] Fixes of mc_wheel_scroll().

 * The accumulated wheel delta has been computed in an undefined way.
   (a % b for negative values can lead to either sign of result with
   different compilers).
 * We reset the accumulated wheel delta if we scroll for at least
   single line. This fixes the visible irregularities in longer slow
   wheel scrollings.

mity/mctrl,mity/mctrl,mity/mctrl,mity/mctrl