libdasc/parse: Implement single-quoted string unquote
libdasc/parse: Implement single-quoted string unquote

beni55/elvish,ke7ofi/elvish,elves/elvish,CodyGuo/elvish,ke7ofi/elvish,CodyGuo/elvish,elves/elvish,beni55/elvish,elves/elvish,elves/elvish,elves/elvish