As part of BUG@39934 fix, the public:
 - THD::current_stmt_binlog_row_based 
variable had been removed and replaced by a private variable:
 - THD::current_stmt_binlog_format. 

THD was refactored and some modifiers and accessors were
implemented for the new variable.

However, due to a bad merge, the
THD::current_stmt_binlog_row_based variable is back as a public
member of THD. This in itself is already potentially
harmful. What's even worse is that while merging some more
patches and resolving conflicts, the variable started being used
again, which is obviously wrong.

To fix this we:
  1. remove the extraneous variable from sql_class.h
  2. revert a bad merge for BUG#49132
  3. merge BUG#49132 properly again (actually, making use of the
     cset used to merge the original patch to mysql-pe).