The following procedure was not possible if max_sp_recursion_depth is 0
create procedure show_proc() show create procedure show_proc;
  
Actually there is no recursive call but the limit is checked.
  
Solved by temporarily increasing the thread's limit just before the fetch from cache
and decreasing after that.


mysql-test/r/sp.result:
  update result
mysql-test/t/sp.test:
  Test for bug #21416 SP: Recursion level higher than zero needed for non-recursive call
sql/sp.cc:
  Increase the max_sp_recursion_depth temporarily for SHOW CREATE PROCEDURE call.
  This call is in fact not recursive but is counted as such. Outcome, it will work
  always but if max_sp_recursion_depth is reached we are going to cache one more
  sp_head instance.