Cleaned up `InitMonsterGFX` by changing the signature of LoadMissileGFX to fit.

Source/missiles.cpp

@@ -2122,7 +2122,7 @@ void __fastcall SetMissDir(int mi, int dir)
 // TODO: replace `int mi` parameter with `missile_graphic_id mi`
 // to enable the compiler to optimize int to char properly
 // check for example the calls in `InitMonsterGFX`
-void __fastcall LoadMissileGFX(int mi)
+void __fastcall LoadMissileGFX(BYTE mi)
 {
 	MisFileData *v1; // esi
 	unsigned char *v2; // eax

Source/missiles.h

@@ -29,7 +29,7 @@ bool __fastcall Plr2PlrMHit(int pnum, int p, int mindam, int maxdam, int dist, i
 void __fastcall CheckMissileCol(int i, int mindam, int maxdam, bool shift, int mx, int my, int nodel);
 void __fastcall SetMissAnim(int mi, int animtype);
 void __fastcall SetMissDir(int mi, int dir);
-void __fastcall LoadMissileGFX(int mi);
+void __fastcall LoadMissileGFX(BYTE mi);
 void __cdecl InitMissileGFX();
 void __fastcall FreeMissileGFX(int mi);
 void __cdecl FreeMissiles();