Add an Array::Alloc convenience for the compiler.

Change-Id: Ie65321d7439ac0ff0b4a39cb507710df088baa6d
diff --git a/src/object.h b/src/object.h
index 8efa059..ca09d07 100644
--- a/src/object.h
+++ b/src/object.h
@@ -604,6 +604,10 @@
     return sizeof(Array) + component_count * component_size;
   }
 
+  // A convenience for code that doesn't know the component size,
+  // and doesn't want to have to work it out itself.
+  static Array* Alloc(Class* array_class, size_t component_count);
+
   static Array* Alloc(Class* array_class,
                       size_t component_count,
                       size_t component_size) {