perfschema: use correct type for left shifts

set_item() uses 1UL << bit, so is_set_item() must do the same.

This fixes sporadic perfschema.show_aggregate failures
(sporadic, because `bit` is the thread id, so depending on how many
tests were run before perfschema.show_aggregate it can be above or
below 32).

storage/perfschema/pfs_engine_table.cc

@@ -226,7 +226,7 @@ bool PFS_table_context::is_item_set(ulong n)
 {
   ulong word= n / m_word_size;
   ulong bit= n % m_word_size;
-  return (m_map[word] & (1 << bit));
+  return (m_map[word] & (1UL << bit));
 }