STATEMENTES END UP IN BINLOG

Problem
=======
If storage engine supports RBR, we allow unsafe SQL statements into
the binlog and a warning is logged in the error log when
binlog_format= STATEMENT. But, the behavior is completely different
when storage engine doesn't support RBR i.e, when binlog_format=
STATEMENT, the query execution is interrupted and errored out with
ER_BINLOG_UNSAFE_AND_STMT_ENGINE even though it can be logged in
statement format.

This behavior is different from the documentation.
See https://dev.mysql.com/doc/refman/5.6/en/binary-log-mixed.html

Fix
===
This patch aims at adding a check on binlog_format before calling
my_error() and sets the appropriate warning flags if the command is
found to be unsafe. So, unsafe SQL statements are now logged with a
warning in the error log if binlog_format= STATEMENT and if storage
engine is only capable of logging in statement format.

Reviewed by Pedro Figueiredo <pedro.figueiredo@oracle.com>>
Reviewed by Bill Qu <bill.qu@oracle.com>