Make fast_exp take an Isolate* paramter

src/codegen.h

Index: src/codegen.h
diff --git a/src/codegen.h b/src/codegen.h
index 7019d3d106e73810e92483a0c8b4e5842aa8a352..c145c223e213f1e8a58502d875a8a7c601156126 100644
--- a/src/codegen.h
+++ b/src/codegen.h
@@ -90,20 +90,21 @@ class CodeGenerator {
 // from the one we use in our generated code.  Therefore we use the same
 // generated code both in runtime and compiled code.
 typedef double (*UnaryMathFunction)(double x);
+typedef double (*UnaryMathFunctionWithIsolate)(double x, Isolate* isolate);
 
-UnaryMathFunction CreateExpFunction();
+UnaryMathFunctionWithIsolate CreateExpFunction(Isolate* isolate);
 UnaryMathFunction CreateSqrtFunction();
 
 
 double modulo(double x, double y);
 
 // Custom implementation of math functions.
-double fast_exp(double input);
+double fast_exp(double input, Isolate* isolate);
 double fast_sqrt(double input);
 #ifdef _WIN64
 void init_modulo_function();
 #endif
-void lazily_initialize_fast_exp();
+void lazily_initialize_fast_exp(Isolate* isolate);
 void init_fast_sqrt_function();