when printing SET @var in mysqlbinlog, backtick the collation (as BINARY is a reserved word)


mysql-test/r/ctype_ucs.result:
  backticks added
mysql-test/r/user_var.result:
  backticks added
mysql-test/t/user_var.test:
  testing a variable with BINARY collation, which needs the backticks
sql/log_event.cc:
  when printing SET @var in mysqlbinlog, backtick the collation (as BINARY is a reserved word)