libutils: Fix missing definition of shared_ptr and unique_ptr

This includes memory header for shared_ptr and unique_ptr templates.
Fixes the following errors:

RefBase.h:803:1: error: ‘shared_ptr’ does not name a type
RefBase.h:810:1: error: ‘unique_ptr’ does not name a type

Change-Id: I6a7a67333c9ef05250c5a3c6199d7fac288f946b