and bug#8849 "problem with insert statement with table alias's": 
make equality propagation work in stored procedures and prepared 
statements.
Equality propagation can change AND/OR structure of ON expressions,
so the fix is to provide each execution of PS/SP with it's own
copy of AND/OR tree. We have been doing that already for WHERE clauses,
now ON clauses are also copied.


mysql-test/r/ps.result:
  Bug#8115: test results fixed.
mysql-test/r/sp.result:
  Bug#8849: test results fixed.
mysql-test/t/ps.test:
  A test case for Bug#8115 "Server Crash with prepared statement".
mysql-test/t/sp.test:
  A test case for Bug#8849 "problem with insert statement with table 
  alias's".
sql/item_cmpfunc.cc:
  Comment a parse tree transformation.
sql/item_cmpfunc.h:
  Comment how Item_equal works with PS/SP.
sql/mysql_priv.h:
  Add declaration for init_stmt_after_parse.
sql/sp_head.cc:
  Call init_stmt_after_parse in restore_lex(), which is used to
  grab TABLE_LIST and SELECT_LEX list of a parsed substatement of
  stored procedure. This is a necessary post-init step which 
  must be done for any statement which can be executed many times.
sql/sql_prepare.cc:
  Implement init_stmt_after_parse() which prepares AND/OR
  structure of all ON expressions and WHERE clauses of a statement
  for copying.
sql/sql_select.cc:
  Implementation of equality propagation inspected with regard to 
  prepared statements and stored procedures. We now restore
  AND/OR structure of every ON expression in addition to AND/OR
  structure of WHERE clauses when reexecuting a PS/SP.
sql/table.h:
  Add declaration for TABLE::prep_on_expr.