NOT FOUND ...' in conditional handled incorrectly".

Whenever we remove an instruction during optimization, we need to
adjust instruction numbers (ip - instruction pointer) stored in all
instructions. In addition to that, sp_instr_hpush_jump, which 
corresponds to DECLARE CONTINUE HANDLER needs adjustment for m_handler,
which holds the number of instruction with the continue handler.
In the bug report, a wrong ip stored in m_handler was pointing at 
FETCH, which resulted in an error message and abnormal SP termination.
The fix is to just remove m_handler member from sp_instr_hpush_jump,
as it's always points to the instruction next to the DECLARE
statement itself (m_ip+1).


mysql-test/r/sp.result:
  Test results fixed (Bug#12168)
mysql-test/t/sp.test:
  A test case for Bug#12168 "'DECLARE CONTINUE HANDLER FOR NOT
  FOUND ...' in conditional handled incorrectly"
sql/sp_head.cc:
  Remove m_handler (the number of continue handler instruction)
  as it always equal to m_ip+1
sql/sp_head.h:
  Remove m_handler (the number of continue handler instruction)
  as it always equal to m_ip+1