fix #H261 - bias in Bresenham's algorithm in walk_path

fix #H261 - bias in Bresenham's algorithm in walk_path

     From a bug report, walk_path() was
favoring orthogonal steps at beginning of the path and diagonal ones at
end, when intermixing diagonal and orthoganal produced a more accurate
representation of the real path.  Only mattered for long distance jumps
3x2 or 3x1 steps away; hurtling always moves in a straight line and short
(2x1 knight) jumps aren't affected by the patch supplied with the report.