Enable the interactive mode if the shell is invoked with the `-s` option and an operand with stdin and stderr connected to a terminal

[magicant]

Currently, yash does not start in the interactive mode if all of the following conditions are true on invocation:

• The -s option is specified on the command line,
• One or more operands (i.e. positional parameters) are specified on the command line, and
• Stdin and stderr are connected to a terminal.

POSIX expects the shell to start in the interactive mode in this situation.