Use first, not last, long name in usage message

[eyalroz]

After the fix for #240 is in, the library must choose a long option for the program usage information.

At the moment, it's not quite clear to me which logic it uses to select a long name - but it's not always choosing the first, nor always choosing the last.

[jarro2783]

I'll take a look at that, I hope it's not putting it into an unordered map or something.