Make _pSLvlVisited into a boolean.

_pSLvlVisited is only ever used in boolean contexts.

Source/loadsave.cpp

@@ -598,7 +598,7 @@ void SaveLevel()
 	if (setlevel == 0)
 		plr[myplr]._pLvlVisited[currlevel] = TRUE;
 	else
-		plr[myplr]._pSLvlVisited[setlvlnum] = 1;
+		plr[myplr]._pSLvlVisited[setlvlnum] = TRUE;
 }
 
 void LoadLevel()

Source/player.cpp

@@ -632,7 +632,7 @@ void CreatePlayer(int pnum, char c)
 	}
 
 	for (i = 0; i < 10; i++) {
-		plr[pnum]._pSLvlVisited[i] = 0;
+		plr[pnum]._pSLvlVisited[i] = FALSE;
 	}
 
 	plr[pnum]._pLvlChanging = FALSE;

structs.h

@@ -277,7 +277,7 @@ typedef struct PlayerStruct {
 	int _pVar7;
 	int _pVar8;
 	BOOLEAN _pLvlVisited[NUMLEVELS];
-	unsigned char _pSLvlVisited[NUMLEVELS]; // only 10 used
+	BOOLEAN _pSLvlVisited[NUMLEVELS]; // only 10 used
 	int _pGFXLoad;
 	unsigned char *_pNAnim[8];
 	int _pNFrames;