Options with variable arity should stop consuming on custom end-of-options delimiter

[remkop]

Options with arity = "*" currently stop consuming arguments when they encounter the default end-of-options delimiter --.

The end-of-options delimiter can be customized since #359, but the logic above was not modified to use the specified end-of-options delimiter and is still hard-coded to the default delimiter.

This was discovered while investigating #718.