Caused by rB43bc494892c3, moving this 'new id' relink to generic
remapping code added the over-head of proper, generic post-processing,
compared to the special-cases previous code was only designed to handle.
Fortunately with recent 'multi-remapping' work we can easily rewrite
that new id relink code to use the multi-remapping approach too.
No behavioral change is expected from this commit, besides the improved
performances (essentially restored to what they where before
rB43bc494892c3).
17906794f5