alloc/raw/linear: add offset overload for views

alloc/raw/linear.hpp

@@ -52,6 +52,13 @@ namespace util::alloc::raw {
 
         size_t offset (const void*) const;
 
+        template <typename T>
+        size_t
+        offset (util::view<T*> ptr) const
+        {
+            return offset (ptr.data ());
+        }
+
         void reset (void);
 
         size_t capacity (void) const;