Fix the I/O for Polyhedral_mesh_domain_3

Mesh_3/include/CGAL/Polyhedral_mesh_domain_3.h

@@ -56,6 +56,10 @@
 # include <tbb/enumerable_thread_specific.h>
 #endif
 
+// To handle I/O for Surface_patch_index if that is a pair of `int` (the
+// default)
+#include <CGAL/internal/Mesh_3/Handle_IO_for_pair_of_int.h>
+
 namespace CGAL {
 
 namespace Mesh_3 {