UPDATE clause conflicts with SELECT for use of item_list field.
  Alter UPDATE clause to use new lex field update_list
  Tests included


mysql-test/r/insert_update.result:
  WL#2274
    New tests for INSERT..SELECT..UPDATE
mysql-test/t/insert_update.test:
  WL#2274
    New tests for INSERT..SELECT..UPDATE
sql/mysql_priv.h:
  Remove function - insert_select_precheck()
sql/sql_class.h:
  WL#2274
    New constructor for class select_insert
sql/sql_insert.cc:
  WL#2274
    Move code into mysql_prepare_insert
    Add checks as param values may be NULL
sql/sql_lex.cc:
  WL#2274
    initialize lex->update_list
sql/sql_lex.h:
  WL#2274
    New field in LEX: update_list
sql/sql_parse.cc:
  WL#2274
    INSERT..UPDATE clause now populates lex->update_list
    Remove redundant function: insert_select_precheck()
sql/sql_prepare.cc:
  WL#2274
    invoke insert_precheck() instead of insert_select_precheck()
sql/sql_yacc.yy:
  WL#2274
    Enable INSERT..SELECT..UPDATE syntax
    New rule - insert_update_list, to populate lex->update_list