PROPERLY QUOTED IN BINLOG FILE
Problem: In load data file query, User variables are allowed
inside "Into_list" and "Set_list". These user variables used
inside these two lists are not properly guarded with backticks
while server is writting into binlog. Hence user variable names
like a` cannot be used in this context.

Fix: Properly quote these variables while
writting into binlog

mysql-test/r/func_compress.result:
  changing result file
mysql-test/r/variables.result:
  changing result file
mysql-test/suite/binlog/r/binlog_stm_mix_innodb_myisam.result:
  changing result file
sql/item_func.cc:
  Quote the user variable items