Fix T73469: OSL: Vector Math Node modulo uses wrong function

This also fixes glsl version of fmod when both inputs are negative.

Differential Revision: https://developer.blender.org/D6704

intern/cycles/kernel/shaders/node_vector_math.osl

@@ -92,7 +92,7 @@ shader node_vector_math(string type = "add",
     Vector = ceil(Vector1);
   }
   else if (type == "modulo") {
-    Vector = mod(Vector1, Vector2);
+    Vector = fmod(Vector1, Vector2);
   }
   else if (type == "fraction") {
     Vector = Vector1 - floor(Vector1);