Enable JS1.7 features in JSSh. Not part of default builds.

extensions/jssh/nsJSSh.cpp

@@ -583,6 +583,9 @@ NS_IMETHODIMP nsJSSh::Init()
   // Enable e4x:
   JS_SetOptions(mJSContext, JS_GetOptions(mJSContext) | JSOPTION_XML);
   
+  // Enable js1.7 features (let, yield, etc - see bug#351515)
+  JS_SetVersion(mJSContext, JSVERSION_1_7);
+  
   mContextStack = do_GetService("@mozilla.org/js/xpc/ContextStack;1");
   if (!mContextStack) {
     NS_ERROR("failed to get the nsThreadJSContextStack service");