The general log write function (general_log_print) uses printf style
arguments which need to be pre-processed, meaning that the all arguments
are copied to a single buffer and the problem is that the buffer size is
constant (1022 characters) but queries can be much larger then this.

The solution is to introduce a new log write function that accepts a
buffer and it's length as arguments. The function is to be used when
a formatted output is not required, which is the case for almost all
query write-to-log calls.

This is a incompatible change with respect to the log format of prepared
statements.


mysql-test/r/log_tables.result:
  Add test case result for Bug#21557
mysql-test/t/log_tables.test:
  Add test case for Bug#21557
sql/log.cc:
  Introduce the logger function general_log_write which is similar to
  general_log_print but accepts a single buffer and the buffer length.
  The function doesn't perform any formatting and sends the buffer
  directly to the underlying log handlers.
sql/log.h:
  Introduce the logger function general_log_write.
sql/log_event.cc:
  Pass the query buffer directly to the logger function, formatting
  is not required on this case.
sql/mysql_priv.h:
  Prototype for the logger function general_log_write.
sql/sp_head.cc:
  Pass the query buffer directly to the logger function, formatting
  is not required on this case.
sql/sql_parse.cc:
  Pass the buffer directly to the logger function when formatting
  is not required.
sql/sql_prepare.cc:
  Don't log the statement id, it avoids making a extra copy of the query
  and the query is not truncated anymore if it exceeds the limit.