Common: Delete Pool's copy constructor and copy/move assignment operators (#117)

The language defines a copy constructor as:

TypeName(const TypeName&)

so this was just deleting a constructor variant that would catch most cases of attempted copies.

src/common/memory_pool.h

@@ -21,9 +21,12 @@ public:
     Pool(size_t object_size, size_t initial_pool_size);
     ~Pool();
 
-    Pool(Pool&) = delete;
+    Pool(const Pool&) = delete;
     Pool(Pool&&) = delete;
 
+    Pool& operator=(const Pool&) = delete;
+    Pool& operator=(Pool&&) = delete;
+
     /// Returns a pointer to an `object_size`-bytes block of memory.
     void* Alloc();