If LOAD DATA INFILE featured a SET clause, the name=value pairs
would be regenerated using item::print. Unfortunately, that code
is mostly optimized for EXPLAIN EXTENDED output and such, and can
not be relied on to return valid SQL.

We now name each value its original, user-supplied form and use
that to create LOAD DATA INFILE statements for statement-based
replication.

mysql-test/suite/binlog/r/binlog_stm_mix_innodb_myisam.result:
  minor change in syntactic sugar
mysql-test/suite/rpl/r/rpl_loaddatalocal.result:
  add test case
mysql-test/suite/rpl/t/rpl_loaddatalocal.test:
  add test case
sql/sql_load.cc:
  Do not try to item::print values in LOAD DATA INFILE's
  SET clause; they might not even be valid SQL at this
  point. Use our saved version instead.
sql/sql_yacc.yy:
  If LOAD DATA INFILE has SET name=val clauses, tag the
  individual val-parts with the user's version so we can
  later replicate that, rather than the smashed pieces
  we'd get from item::print once the optimizer's through
  with our poor values.