Use the standard C INFINITY and NAN constants directly

The `Math_INF` and `Math_NAN` defines were just aliases for those
constants, so we might as well use them directly.

Some portions of the code were already using `INFINITY` directly.

modules/visual_script/visual_script_nodes.cpp

@@ -2182,8 +2182,8 @@ double VisualScriptMathConstant::const_value[MATH_CONSTANT_MAX] = {
 	Math_TAU,
 	2.71828182845904523536,
 	Math::sqrt(2.0),
-	Math_INF,
-	Math_NAN
+	INFINITY,
+	NAN
 };
 
 int VisualScriptMathConstant::get_output_sequence_port_count() const {