Fixed the between-objects sorting problem previously mentioned in the merge...

Fixed the between-objects sorting problem previously mentioned in the merge request. Now they're sorted by whichever sprite has an end closest to the camera, instead of the middle point previously used.

http://i.imgur.com/UyOKX5u.png <-- this common glitch with crawlas given MF_PAPER (THEY'RE NOT GOOD AT TURNING NEAR EDGES) used to show the behind-crawlas in front of the front-crawlas.

Unfortunately, I've just discovered this issue (which happens with the old version of the sorting code too): http://i.imgur.com/QNjbATB.png but to be fair these crawlas have gotten stuck inside the edges of this platform, so I'm not sure I can do anything about this without cutting off Sonic's feet when he stands on the ground? shrug