Fix the linux build by removing the name alias that does not agree with gcc4.9

Author: nadavrot

include/glow/IR/IR.h

@@ -56,8 +56,6 @@ class Value : public Named,
               public Typed,
               public Kinded {
 public:
-  using Use = Use;
-
   Value(TypeRef T, Kinded::Kind k) : Typed(T), Kinded(k) {}
 };
 

src/glow/Optimizer/IROptimizer.cpp

@@ -84,7 +84,7 @@ static void replaceAllNonDeallocUsersWith(Value *val, Value *with) {
   auto &users = val->getUsers();
   // We use a vector here because changing the operands of the user changes the
   // uselist, and this invalidates the iterator.
-  std::vector<Value::Use> usersVec(users.begin(), users.end());
+  std::vector<Use> usersVec(users.begin(), users.end());
   for (auto &U : usersVec) {
     // Ignore dealloc instrs.
     if (isa<DeallocActivationInst>(U.get())) {