fixup! io: factor out alignment operation

Author: pcanal

roottest/root/meta/alignment/emulation.C

@@ -5,6 +5,8 @@
 #include <cassert>
 #include "TError.h"
 #include "TFile.h"
+#include "TBuffer.h"
+#include "TObjArray.h"
 
 // Containee type with a custom alignment (over-aligned)
 struct alignas(256) Containee {