Make Error.prototype.toString spec compliant; and fix various side-effect-free error printing metho…

test/mjsunit/regress/regress-crbug-523308.js

Index: test/mjsunit/regress/regress-crbug-523308.js
diff --git a/test/mjsunit/regress/regress-crbug-523308.js b/test/mjsunit/regress/regress-crbug-523308.js
index 5715762ed6b57e98c45e551fa6483bd8e5501a34..36114791b9dccba45920dc54481a4a7b51f37554 100644
--- a/test/mjsunit/regress/regress-crbug-523308.js
+++ b/test/mjsunit/regress/regress-crbug-523308.js
@@ -6,5 +6,4 @@ var error;
 try { reference_error(); } catch (e) { error = e; }
 toString = error.toString;
 error.__proto__ = [];
-assertEquals("ReferenceError: reference_error is not defined",
-             toString.call(error));
+assertEquals("Error: reference_error is not defined", toString.call(error));