[perl #116895] [BUG] LTM alternation captures the wrong stuff when backtracking in Rakudo

[Christian Bartolomaeus via RT]

Looks like this was fixed for Moar (because of jnthn++'s work for RT #125285).

$ perl6-m -e 'say "abcde" ~~ / (a | b | bc | cde)+»/'
｢abcde｣
 0 => ｢a｣
 0 => ｢b｣
 0 => ｢cde｣

I added a test (fudged 'todo' for JVM) to S05-match/capturing-contexts.t with 
commit https://github.com/perl6/roast/commit/82d271359f.