early update literals

early update literals

for better cost estimation in the following series for matches.

Unfortunately, this does not necessarily result in better compression.
Results are all over the places,
with best outcome observed for silesia/x-ray
but most other files tend to get slightly worse after this change.

It's strange because it seems that we are just providing more accurate information for the cost estimator.

Anyway, as it also increases code complexity,
it's probably not interesting enough for now.