Move generated math methods from platform to codegen

src/codegen.h

Index: src/codegen.h
diff --git a/src/codegen.h b/src/codegen.h
index 1e87a1b9e7654feddd63ab869ad43a055733b609..b70665db2849fb71ce6eee134ff1bd6625805c38 100644
--- a/src/codegen.h
+++ b/src/codegen.h
@@ -99,6 +99,18 @@ UnaryMathFunction CreateExpFunction();
 UnaryMathFunction CreateSqrtFunction();
 
 
+double modulo(double x, double y);
+
+// Custom implementation of math functions.
+double fast_exp(double input);
+double fast_sqrt(double input);
+#ifdef _WIN64
+void init_modulo_function();
+#endif
+void lazily_initialize_fast_exp();
+void init_fast_sqrt_function();
+
+
 class ElementsTransitionGenerator : public AllStatic {
  public:
   // If |mode| is set to DONT_TRACK_ALLOCATION_SITE,