[perl #120449] Interpolation at edge of quoteword items cancels out inter-item space

[Christian Bartolomaeus via RT]

This works now as expected -- e.g.:

$ perl6 -e 'my $x = 2; say «1 $x 3»'
(1 2 3)

$ perl6 -e 'say «{4 + 2} 4+2»'
(6 4+2)

I added a test to S02-literals/string-interpolation.t with commit 
https://github.com/perl6/roast/commit/8e47b673bec81eefb547f768c84a390332c51aca

I'm closing this ticket as 'resolved'.