[perl #118467] [BUG] Required named occurring before slurpy wrongly considered a multi candidate in Rakduo

[Christian Bartolomaeus via RT]

There already was a (skipped) test for this bug in 
S06-multi/positional-vs-named.t

I added a reference to this ticket with commit 
https://github.com/perl6/roast/commit/d397bca9f2