add boolean command-line option --autocommit.

mysql-test/mysql-test-run.pl:
  do in --gdb like in --ddd: to let the developer debug the startup
  phase (like command-line options parsing), don't "run".
  It's the third time I do this change, it was previously lost
  by merges, port of 6.0 to next-mr...
mysql-test/r/mysqld--help-notwin.result:
  new command-line option
mysql-test/r/mysqld--help-win.result:
  a Linux user's best guess at what the Windows result should be
mysql-test/suite/sys_vars/inc/autocommit_func2.inc:
  new test
mysql-test/suite/sys_vars/t/autocommit_func2-master.opt:
  test new option
mysql-test/suite/sys_vars/t/autocommit_func3-master.opt:
  test new option
sql/mysqld.cc:
  new --autocommit
sql/mysqld.h:
  new --autocommit
sql/sql_partition.cc:
  What matters to this partitioning quote is to have
  the OPTION_QUOTE_SHOW_CREATE flag down, it's all
  that append_identifier() uses. So we make it explicit.