Fix `numoflines` calculations in sectorlines_* functions by first typecasting...

Fix `numoflines` calculations in sectorlines_* functions by first typecasting seclines (the sector.lines address) to size_t before doing any math on it, then (after the math) typecast the result to size_t * and dereference it.

And yes, this time I tested it to make sure it works :)

src/lua_maplib.c

@@ -445,7 +445,7 @@ static int sectorlines_get(lua_State *L)
 	// get the "linecount" by shifting our retrieved memory address of "lines" to where "linecount" is in the sector_t, then dereferencing the result
 	// we need this to determine the array's actual size, and therefore also the maximum value allowed as an index
 	// this only works if seclines is actually a pointer to a sector's lines member in memory, oh boy
-	numoflines = (size_t)(*(seclines - (offsetof(sector_t, lines) - offsetof(sector_t, linecount))));
+	numoflines = (size_t)(*(size_t *)(((size_t)seclines) - (offsetof(sector_t, lines) - offsetof(sector_t, linecount))));
 
 /* OLD HACK
 	// check first linedef to figure which of its sectors owns this sector->lines pointer
@@ -479,7 +479,7 @@ static int sectorlines_num(lua_State *L)
 		return luaL_error(L, "accessed sector_t.lines doesn't exist anymore.");
 
 	// see comments in the _get function above
-	numoflines = (size_t)(*(seclines - (offsetof(sector_t, lines) - offsetof(sector_t, linecount))));
+	numoflines = (size_t)(*(size_t *)(((size_t)seclines) - (offsetof(sector_t, lines) - offsetof(sector_t, linecount))));
 	lua_pushinteger(L, numoflines);
 	return 1;
 }