Fixed typos and made all assert functions optional

src/modelinfo/VehicleModelInfo.h

@@ -124,6 +124,4 @@ public:
 	static void SetComponentsToUse(int8 c1, int8 c2) { ms_compsToUse[0] = c1; ms_compsToUse[1] = c2; }
 };
 
-#ifdef CHECK_STRUCT_SIZES
-static_assert(sizeof(CVehicleModelInfo) == 0x1F8, "CVehicleModelInfo: error");
-#endif
+VALIDATE_SIZE(CVehicleModelInfo, 0x1F8);