Changed names of multi-source log files so that original suffixes are kept.


include/my_sys.h:
  Added fn_ext2(), which returns pointer to last '.' in file name
mysql-test/extra/rpl_tests/rpl_max_relay_size.test:
  Updated test
mysql-test/suite/multi_source/info_logs-master.opt:
  Test with strange file names
mysql-test/suite/multi_source/info_logs.result:
  Updated results
mysql-test/suite/multi_source/info_logs.test:
  Changed to test with complex names to be able to verify the filename generator code
mysql-test/suite/multi_source/relaylog_events.result:
  Updated results
mysql-test/suite/multi_source/reset_slave.result:
  Updated results
mysql-test/suite/multi_source/skip_counter.result:
  Updated results
mysql-test/suite/multi_source/skip_counter.test:
  Added testing of max_relay_log_size
mysql-test/suite/rpl/r/rpl_row_max_relay_size.result:
  Updated results
mysql-test/suite/rpl/r/rpl_stm_max_relay_size.result:
  Updated results
mysql-test/suite/sys_vars/r/max_relay_log_size_basic.result:
  Updated results
mysql-test/suite/sys_vars/t/max_relay_log_size_basic.test:
  Updated results
mysys/mf_fn_ext.c:
  Added fn_ext2(), which returns pointer to last '.' in file name
sql/log.cc:
  Removed some wrong casts
sql/log.h:
  Updated comment to reflect new code
sql/log_event.cc:
  Updated DBUG_PRINT
sql/mysqld.cc:
  Added that max_relay_log_size copies it's values from max_binlog_size
sql/mysqld.h:
  Removed max_relay_log_size
sql/rpl_mi.cc:
  Changed names of multi-source log files so that original suffixes are kept.
sql/rpl_mi.h:
  Updated prototype
sql/rpl_rli.cc:
  Updated comment to reflect new code
  Made max_relay_log_size depending on master connection.
sql/rpl_rli.h:
  Made max_relay_log_size depending on master connection.
sql/set_var.h:
  Made option global so that one can check and change min & max values (sorry Sergei)
sql/sql_class.h:
  Made max_relay_log_size depending on master connection.
sql/sql_repl.cc:
  Updated calls to create_signed_file_name()
sql/sys_vars.cc:
  Made max_relay_log_size depending on master connection.
  Made old code more reusable
sql/sys_vars.h:
  Changed Sys_var_multi_source_uint to ulong to be able to handle max_relay_log_size
  Made old code more reusable