GetoptMode = true suppresses help.

**Describe the bug**
var parser = new Parser(opts => { opts.GetoptMode = true; });
result = parser.ParseArguments....

opts.GetoptMode = true causes the help to be suppressed

**To Reproduce**
Make your own "new Parser" with only GetoptMode = true

**Expected behavior**
The help should show up regardless

**Screenshots**
If applicable, add screenshots to help explain your problem.

**Additional context**
Appending other options to "new Parser" didn't seem to help.

Start with the Parser construction and ParseArguments call shown in the report, then trace how GetoptMode affects help handling. Reproduce the issue with a parser configured only with GetoptMode = true and compare the help output with the default parser. Done when help is shown in that configuration and a regression test covers it.

Written by the indexing model from the issue text.