Devirtualizing Value destructor (PR889). Patch by Pawel Kunio!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@44747 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/GlobalAlias.h

@@ -43,6 +43,11 @@ class GlobalAlias : public GlobalValue {
   const GlobalAlias *getPrev() const { return Prev; }
 
   Use Aliasee;
+protected:
+  static void destroyThis(GlobalAlias*v) {
+    GlobalValue::destroyThis(v);
+  }
+  friend class Value;
 public:
   /// GlobalAlias ctor - If a parent module is specified, the alias is
   /// automatically inserted into the end of the specified module's alias list.