Pixel Movement

I just posted another update. Here is a list of the changes:

• Fixed runtime errors that were caused by the mob's move_towards proc.
• Added another benchmark (the benchmarks\demo-2 folder) that creates a configurable number of mobs that continuously call move_to. The destination of their moves is a random turf within a configurable distance from their current location.
• Changed the move() proc and action() proc to support diagonal movement. The mob's direction will now be changed to a diagonal (ex: NORTHEAST) if the player is holding both of the corresponding arrow keys.
• These changes also fix a problem with limiting the player's speed. Previously, if a player's move_speed was 5, moving in a diagonal would make vel_x = 3.2 and vel_y = 3.7 when they should really be equal. Now they will be equal (both will be about 3.53).

The big point is the third one: The changes to move() and action() make the library support 8-directional mob icons and it fixes a problem that had existed with diagonal movement (as described in the last bulleted point).

Also, the v3.1 update had changed the way fractional movement worked and this appears to have fixed some camera issues. With the camera mode set to SLIDE, there used to be some cases where the camera would be jittery, but this seems to have stopped (I always suspected it was caused by having decimal values of pixel_x and pixel_y).