🎨 Apply direction enum to monsters and relations

Missiles _mimfnum is being used for a lot more then just directions and
can also be a 16 degree direction so can't apply enum verbs and
restricitons to it in most cases. This in turns also affects SetMissDir
and some other functions that have to stay int.

Source/dead.cpp

@@ -76,7 +76,7 @@ void InitDead()
 	assert(nd <= MAXDEAD);
 }
 
-void AddDead(int dx, int dy, int8_t dv, int ddir)
+void AddDead(int dx, int dy, int8_t dv, direction ddir)
 {
 	dDead[dx][dy] = (dv & 0x1F) + (ddir << 5);
 }