Affordances for "local maxima" in coverage

clusterfuzz has various strategies to try to handle the problem of getting stuck in a local maxima for coverage.

clusterfuzzlite doesn't appear to have these, as a result some fuzzers may find themselves stuck, unable to make progress.

I believe https://github.com/alex/rust-asn1 is experiencing this. The fuzzer is not making much progress, however if I blow away all coverage and run it from the start I can often get it to advance further.