Fix offset aim when using freelook and r_screensize is 8

Fixes #836. Thanks @Krypcik13ty!

src/p_local.h

@@ -103,7 +103,7 @@ void P_SetPlayerSprite(const size_t position, const statenum_t stnum);
 // 16 pixels of bob
 #define MAXBOB              0x100000
 #define MLOOKUNIT           8
-#define PLAYERSLOPE(a)      ((((a)->lookdir / MLOOKUNIT) << FRACBITS) / (VANILLAWIDTH / 2))
+#define PLAYERSLOPE(a)      ((((a)->lookdir / MLOOKUNIT) << FRACBITS) / (r_screensize == r_screensize_max ? 140 : 160))
 
 extern bool autousing;
 extern int  deadlookdir;