rust-cpython: add generation counter to leaked reference
This counter increments on borrow_mut() to invalidate existing leaked
references. This is modeled after the iterator invalidation in Python.
The other checks will be adjusted by the subsequent patches.
fixbundle() {
grep -v 'saving bundle' | grep -v 'saved backup' | \
grep -v added | grep -v adding | \
grep -v "unable to find 'e' for patching" | \
grep -v "e: No such file or directory" | \
cat
}