findrenames: first loop over the removed files, it's faster
Getting the file from the working dir is less expensive than getting it from
the repo history, hence the speedup.
benchmarked on crew repo with:
rm -rf * ; hg up -C ; for i in `find . -name "*.py"` ; do mv $i $i.new;done
followed by:
hg addremove -s 100
before: Time: real 68.760 secs (user 65.760+0.000 sys 2.490+0.000)
after : Time: real 28.890 secs (user 26.920+0.000 sys 1.450+0.000)
i18n-pt_BR: synchronized with
5d748045c2ae