"Stored procedures: crash with function calling itself".

Disallow recursive stored routines until we either make Item's and LEX
reentrant safe or will use spearate sp_head instances (and thus separate
LEX objects and Item trees) for each routine invocation.


mysql-test/r/sp-error.result:
  Added tests for bug #11394 "Recursion in SP crash server" and
  bug #11600 "Stored procedures: crash with function calling itself".
  (We simply disallow recursion for stored routines).
mysql-test/r/sp.result:
  Disabled test cases containing recursive stored routines until we will
  support for them.
mysql-test/t/sp-error.test:
  Added tests for bug #11394 "Recursion in SP crash server" and
  bug #11600 "Stored procedures: crash with function calling itself".
  (We simply disallow recursion for stored routines).
mysql-test/t/sp.test:
  Disabled test cases containing recursive stored routines until we will
  support for them.
sql/share/errmsg.txt:
  Added error message saying that recursive stored routines are disallowed.
sql/sp_head.cc:
  sp_head::execute():
    Since many Item's and LEX members can't be used in reentrant fashion
    we have to disable recursion for stored routines. So let us track
    routine invocations using sp_head::m_is_invoked member and raise
    error when one attempts to call routine recursively.
sql/sp_head.h:
  sp_head:
    Added m_is_invoked member for tracking of routine invocations and
    preventing recursion.