Post-push fix.
Problem: After the original bugfix, if a statement is unsafe,
binlog_format=mixed, and engine is statement-only, a warning was
generated and the statement executed. However, it is a fundamental
principle of binlogging that binlog_format=mixed should guarantee
correct logging, no compromise. So correct behavior is to generate
an error and don't execute the statement.
Fix: Generate error instead of warning.
Since issue_unsafe_warnings can only generate one error message,
this allows us to simplify the code a bit too:
decide_logging_format does not have to save the error code for
issue_unsafe_warnings


mysql-test/suite/binlog/r/binlog_statement_insert_delayed.result:
  updated result file
mysql-test/suite/binlog/r/binlog_stm_ps.result:
  updated result file
mysql-test/suite/binlog/r/binlog_stm_unsafe_warning.result:
  updated result file
mysql-test/suite/binlog/r/binlog_unsafe.result:
  updated result file
mysql-test/suite/rpl/r/rpl_stm_found_rows.result:
  updated result file
mysql-test/suite/rpl/r/rpl_stm_loadfile.result:
  updated result file
mysql-test/suite/rpl_ndb/r/rpl_ndb_binlog_format_errors.result:
  updated result file
mysql-test/suite/rpl_ndb/t/rpl_ndb_binlog_format_errors.test:
  updated test:
   - ER_BINLOG_UNSAFE_AND_STMT_ENGINE is now an error.
   - added test for multiple types of unsafety
sql/share/errmsg.txt:
   - Reformulated ER_BINLOG_UNSAFE_AND_STMT_ENGINE to reflect that it
     is now an error, not a warning.
   - Added "Reason for unsafeness" to ER_BINLOG_UNSAFE_STATEMENT and
     ER_BINLOG_UNSAFE_AND_STMT_ENGINE.
sql/sql_class.cc:
  In decide_logging_format:
   - generate an error immediately in case 3, instead of scheduling a
     warning to be generated later. also updated comments accordingly
   - in case 7, there is only one unsafe warning error code now, so we
     don't need to store it in binlog_unsafe_warning_flags
     (see changes in sql_lex.h)
   - fixed compilation warning in DBUG_PRINT
  
  In issue_binlog_warning:
   - moved array of error codes to sql_lex.h (so that they are
     accessible also from decide_logging_format)
   - simplified code after the first set of bits in
     binlog_unsafe_warning_flags was removed
sql/sql_class.h:
   - got rid of enum_binlog_stmt_warning. It's not needed anymore
     since we only have one type of unsafe warning (one of them
     turned into an error)
   - updated comments accordingly
sql/sql_lex.cc:
  added initialization of the array of error codes that has been
  moved from THD::issue_unsafe_warnings to LEX.
sql/sql_lex.h:
  Moved array of error codes from THD::issue_unsafe_warnings to LEX.