Describe the bug
vncviewer.exe no longer supports the MenuKey option. When given it, the error message is quite unhelpful.

To Reproduce

1. Run vncviewer.exe MenuKey=F8 example.net:7

Expected behavior
vncviewer exits with a message such as "Unknown option MenuKey".

Actual behavior
vncviewer exits with error message "Extra argument example.net:7".

Version information
The unwanted behavior described above was introduced in commit af55625.