Fix Vitellary looking left for one frame in "Now Stay Close To Me..."

There's a bug in the cutscene that plays if your companion is Vitellary
in the room "Now Stay Close To Me...". The relevant gamestate is
gamestate 43, which for Vitellary calls the script `int1yellow_4`.

When Vitellary says the text box "That big... C thing! I wonder what it
does?", Terry intended for Vitellary to change his facing direction to
the left, as you can see with the command `changedir(yellow,0)` in the
original scripting. `changedir()` just changes the `dir` attribute of an
entity, and a `dir` of 0 means face left and a `dir` of 1 means face
right.

Then when Vitellary says "Maybe we should take it back to the ship to
study it?", Terry intended for him to face rightwards once again, as
indicated by the `changedir(yellow,1)` command.

Unfortunately, what happens instead is that when Vitellary says the
first text box ("That big... C thing! I wonder what it does?"), he turns
left for precisely one frame, and then afterwards goes back to facing
right. Then the second text box comes around, but he's already facing
right. How come?

Well, the problem here is that Vitellary's AI for "follow Viridian" is
overriding his `dir` attribute. Vitellary's AI says "get close to
Viridian", but Vitellary is already close enough to them that he stays
put. However, he still turns to face them as part of that AI.

To fix that, we need to put him in the AI mode that specifically says to
face left, with the command `changeai(yellow,faceleft)`. That way, he no
longer has the AI mode of following Viridian, and he will actually look
left for the intended duration instead of only looking left for one
frame.

But then we have another problem. When the cutscene ends, Vitellary no
longer follows Viridian. I mean it makes sense - we just placed him in
"only face left" mode, not "follow Viridian" mode! And this is not
merely a visual problem, because Vitellary is a supercrewmate and the
game won't let the player walk off the screen if Vitellary isn't
offscreen yet.

To fix THAT issue, we'll need to put Vitellary back in "follow Viridian"
mode. It turns out that the `changeai()` command was more intended for
scripting crewmates (entity type 12), NOT supercrewmates (entity type
14). As such, the command assumes that you'll want state numbers that
apply to entity type 12, such as 10, 11, 12, 13, and 14, even though the
only one that applies to entity type 14 is state 0, and every other
state number just makes it so that the entity doesn't move an inch. And
specifying faceleft/faceright is just state number 17.

Luckily, we can still pass the raw state number to `changeai()`, we
don't have to use its intended names. So I do a `changeai(yellow,0)` to
set Vitellary's state number back to 0 when it comes time to make him
face right again.

As a bonus, I added comments to the changed lines. This is a semi-obtuse
method of scripting, so it's always good to clarify.

desktop_version/src/Scripts.cpp

@@ -2651,7 +2651,7 @@ void scriptclass::load(const std::string& name)
         "speak_active",
 
         "squeak(yellow)",
-        "changedir(yellow,0)",
+        "changeai(yellow,faceleft)", // changedir(yellow,0) doesn't work
         "text(yellow,0,0,2)",
         "That big... C thing!",
         "I wonder what it does?",
@@ -2676,7 +2676,7 @@ void scriptclass::load(const std::string& name)
         "speak_active",
 
         "squeak(yellow)",
-        "changedir(yellow,1)",
+        "changeai(yellow,0)", // Make him face right again
         "text(yellow,0,0,2)",
         "Maybe we should take it back",
         "to the ship to study it?",