Problem: in mixed and statement mode, a query that refers to a
system variable will use the slave's value when replayed on
slave. So if the value of a system variable is inserted into a
table, the slave will differ from the master.
Fix: mark statements that refer to a system variable as "unsafe",
meaning they will be replicated by row in mixed mode and produce a warning
in statement mode. There are some exceptions: some variables are actually
replicated. Those should *not* be marked as unsafe.
BUG#34732: mysqlbinlog does not print default values for auto_increment variables
Problem: mysqlbinlog does not print default values for some variables,
including auto_increment_increment and others. So if a client executing
the output of mysqlbinlog has different default values, replication will
be wrong.
Fix: Always print default values for all variables that are replicated.
I need to fix the two bugs at the same time, because the test cases would
fail if I only fixed one of them.


include/m_ctype.h:
  Added definition of ILLEGAL_CHARSET_INFO_NUMBER. We just need a symbol
  for a number that will never be used by any charset. ~0U should be safe
  since charset numbers are sequential, starting from 0.
mysql-test/include/commit.inc:
  Upated test to avoid making statements unsafe.
mysql-test/r/commit_1innodb.result:
  Updated test needs updated result file.
mysql-test/r/mysqlbinlog.result:
  Updated result file.
mysql-test/r/mysqlbinlog2.result:
  Updated result file.
mysql-test/r/user_var-binlog.result:
  Updated result file.
mysql-test/suite/binlog/r/binlog_base64_flag.result:
  Updated result file.
mysql-test/suite/binlog/r/binlog_stm_ctype_ucs.result:
  Updated result file.
mysql-test/suite/binlog/r/binlog_unsafe.result:
  Modified test file needs modified result file.
mysql-test/suite/binlog/t/binlog_base64_flag.test:
  Need to filter out pseudo_thread_id from result since it is
  nondeterministic.
mysql-test/suite/binlog/t/binlog_unsafe.test:
  Add tests that using variables is unsafe. The 'CREATE VIEW' tests didn't
  make sense, so I removed them. SHOW WARNINGS is not necessary either,
  because we get warnings for each statement in the result file.
mysql-test/suite/rpl/r/rpl_row_mysqlbinlog.result:
  Updated result file.
mysql-test/suite/rpl/r/rpl_skip_error.result:
  Updated result file.
mysql-test/suite/rpl/t/rpl_skip_error.test:
  The test used @@server_id, which is not safe to replicate, so it would
  have given a warning. The way it used @@server_id was hackish (issue a
  query on master that removes rows only on master), so I replaced it by a
  more robust way to do the same thing (connect to slave and insert the
  rows only there).
  Also clarified what the test case does.
mysql-test/t/mysqlbinlog2.test:
  Use --short-form instead of manually filtering out nondeterministic stuff
  from mysqlbinlog (because we added the nondeterministic @@pseudo_thread_id
  to the output).
sql/item_func.cc:
  Added method of Item_func_get_system_var that indicates whether the given
  system variable will be written to the binlog or not.
sql/item_func.h:
  Added method of Item_func_get_system_var that indicates whether the given
  system variable will be written to the binlog or not.
sql/log_event.cc:
   - auto_increment_offset was not written to the binlog if
  auto_increment_increment=1
   - mysqlbinlog did not output default values for some variables
  (BUG#34732). In st_print_event_info, we remember for each variable whether
  it has been printed or not. This is achieved in different ways for
  different variables:
      - For auto_increment_*, lc_time_names, charset_database_number,
        we set the default values in st_print_event_info to something
        illegal, so that it will look like they have changed the first time
        they are seen.
      - For charset, sql_mode, pseudo_thread_id, we add a flag to
        st_print_event_info which indicates whether the variable has been
        printed.
      - Since pseudo_thread_id is now printed more often, and its value is
        not guaranteed to be constant across different runs of the same
        test script, I replaced it by a constant if --short-form is used.
   - Moved st_print_event_info constructor from log_event.h to log_event.cc,
  since it now depends on ILLEGAL_CHARSET_NUMBER, which is defined in
  m_ctype.h, which is better to include from a .cc file than from a header
  file.
sql/log_event.h:
  Added fields to st_print_event_info that indicate whether some of the
  variables have been written or not. Since the initialization of
  charset_database_number now depends on ILLEGAL_CHARSET_INFO_NUMBER, which
  is defined in a header file, which we'd better not include from this
  header file -- I moved the constructor from here to log_event.cc.
sql/set_var.cc:
  System variables now have a flag binlog_status, which indicates if they
  are written to the binlog. If nothing is specified, all variables are
  marked as not written to the binlog (NOT_IN_BINLOG) when created. In this
  file, the variables that are written to the binlog are marked with
  SESSION_VARIABLE_IN_BINLOG.
sql/set_var.h:
  Added flag binlog_status to class sys_var. Added a getter and a
  constructor parameter that sets it.
  Since I had to change sys_var_thd_enum constructor anyways, I simplified
  it to use default values of arguments instead of three copies of the
  constructor.
sql/sql_yacc.yy:
  Mark statements that refer to a system variable as "unsafe",
  meaning they will be replicated by row in mixed mode. Added comment to
  explain strange piece of code just above.
mysql-test/include/diff_tables.inc:
  New auxiliary test file that tests whether two tables (possibly one on
  master and one on slave) differ.
mysql-test/suite/rpl/r/rpl_variables.result:
  New test case needs new result file.
mysql-test/suite/rpl/r/rpl_variables_stm.result:
  New test file needs new result file.
mysql-test/suite/rpl/t/rpl_variables.test:
  Test that INSERT of @@variables is replicated correctly (by switching to
  row-based mode).
mysql-test/suite/rpl/t/rpl_variables_stm.test:
  Test that replication of @@variables which are replicated explicitly works
  as expected in statement mode (without giving warnings).