Split SetProperty(...attributes, strictmode) into AddProperty(...attributes) and SetProperty(...…

src/symbol.js

Index: src/symbol.js
diff --git a/src/symbol.js b/src/symbol.js
index 1c4830202068c44d6957748d900fdda6fd1360d9..e0dc9ac3b1382e47c45a846c9774447cc28539a7 100644
--- a/src/symbol.js
+++ b/src/symbol.js
@@ -113,7 +113,7 @@ function SetUpSymbol() {
     "keyFor", SymbolKeyFor
   ));
 
-  %SetProperty($Symbol.prototype, "constructor", $Symbol, DONT_ENUM);
+  %DefineProperty($Symbol.prototype, "constructor", $Symbol, DONT_ENUM);
   InstallFunctions($Symbol.prototype, DONT_ENUM, $Array(
     "toString", SymbolToString,
     "valueOf", SymbolValueOf