Bug 623123 - Add constructor for nsXULAppInfo (which inherits from nsIXULAppInfo) to placate CLang; r=bsmedberg

toolkit/xre/nsAppRunner.cpp

@@ -613,6 +613,7 @@ class nsXULAppInfo : public nsIXULAppInfo,
 
 {
 public:
+  nsXULAppInfo() {}
   NS_DECL_ISUPPORTS_INHERITED
   NS_DECL_NSIXULAPPINFO
   NS_DECL_NSIXULRUNTIME