Removed session variables for error injects
started using DBUG macros for error injects


include/my_dbug.h:
  Added new DBUG macros
sql/sql_class.cc:
  Removed session variables for error injects
sql/sql_class.h:
  Removed session variables for error injects
sql/mysql_priv.h:
  Changed ERROR INJECT macros to use DBUG macros
sql/mysqld.cc:
  Removed session variables for error injects
sql/set_var.cc:
  Removed session variables for error injects