In newer versions change was made to the flags: from the documentation:
--extended-insert, -e
Write INSERT statements using multiple-row syntax that includes several VALUES lists. This results in a smaller dump file and speeds up inserts when the file is reloaded.
--opt
This option, enabled by default, is shorthand for the combination of --add-drop-table --add-locks --create-options --disable-keys --extended-insert --lock-tables --quick --set-charset. It gives a fast dump operation and produces a dump file that can be reloaded into a MySQL server quickly.
Because the --opt option is enabled by default, you only specify its converse, the --skip-opt to turn off several default settings. See the discussion of mysqldump option groups for information about selectively enabling or disabling a subset of the options affected by --opt.
--skip-extended-insert
Turn off extended-insert