Changed test suite to use --log-basename (to get the code tested)
Added --sync-sys=1 to test suite to speed it up.
Better error messages if something goes wrong with mysql_install_db


mysql-test/Makefile.am:
  Removed not existing directory
mysql-test/lib/My/ConfigFactory.pm:
  Use log-basename
  We had to also set 'log_error' as some test was explicitely using the old name
  Added 'sync-sys=1' to speed up test suite
mysql-test/r/variables-notembedded.result:
  Updated test results (variable relay_log is now set)
mysql-test/suite/binlog/t/binlog_delete_and_flush_index-master.opt:
  Force specific names for some log files.
mysql-test/suite/binlog/t/binlog_index-master.opt:
  Force specific names for some log files.
mysql-test/suite/binlog/t/binlog_stm_unsafe_warning-master.opt:
  Force specific names for some log files.
mysql-test/suite/binlog/t/binlog_stm_unsafe_warning.test:
  Better error message if something goes wrong
mysql-test/suite/rpl/r/rpl_flushlog_loop.result:
  Updated results
mysql-test/suite/rpl/rpl_1slave_base.cnf:
  Use --log-basename
scripts/mysql_install_db.sh:
  More information to --help
  Write url to knowledge base if something goes wrong
  Fail at once if we can't create a database directory (no reason to continue and write a screenful of not related text)
scripts/mysqld_safe.sh:
  Also allow one to use --data for --datadir (common shortening)
  Added support for --log-basename
  Fail at once if we can't create a log directory
  Fixed bug where we used a pid file name without '.pid' extension
sql/log.cc:
  Create a log file name trough my_once_alloc()  (To get it automaticly freed at exit)
sql/mysql_priv.h:
  Added new prototype
sql/mysqld.cc:
  Added support for --log-basename
  Better help for a lot of log-filename related variables.
sql/rpl_rli.cc:
  Write information that one can use --log-basename
sql/set_var.cc:
  Add log_basename as a readonly variable