[Re-Usable] Sprite Fixes v2.2.16

I shut off a couple of more transparent pixels in Knuckles' skidding sprites that I forgot to address in the last update. That's it, I've got nothing else here. I simply wanted to get this out quickly before moving on to other projects.

Whoops... I forgot to include an important fix for the back of Knuckles' gliding and swimming sprites lacking the same shading on his head and tail between all of the frames of all the animations. I also slightly reshaped the shading at the top there to look a bit better.

This is an update focused on Knuckles since I've been looking at his sprites in greater detail. Here's a quick rundown of what's changed:

- Edited Knuckles' SKIDA4 and SKIDA6 (skidding sprites) to address an issue with a misplaced transparent pixel in the middle of his body;
- Quickly tweaked Knuckles' XTRAB0 (the CSS graphic) to remove a stray white pixel between his shoes which wasn't intended to exist in the first place because it's a part of the image's background which is supposed to be entirely transparent;
- Changed a few of Knuckles' NiGHTs sprites to make his white crescent consistent with his gliding/swimming sprites.

A small update to change a couple of little things. Namely, I've edited regular Sonic's SKIDA5 sprite to make the back of his head match his RUN_A5/RUN_C5 sprites and I changed one pixel in his FALLB4 and FALLB6 on one of his arms to match his other sprites in frame A as well as his super sprites which had that pixel colored differently for whatever reason.

I tweaked the vertical offsets a little for some of Knuckles' springing sprites and gave Super Sonic his mouth in a couple of his stunned sprites since it was missing from them for whatever reason. This last fix was also duplicated to Sonic's NiGHTs sprites since they use the same stunned sprites as Super Sonic.

A tiny change was made to address the fact that Sonic's life icon apparently did not match his actual standing sprite it's based on by about one pixel (specifically on the edge of the eye close to the left border of the image).