Freenet / Hyphanet build 1502/1503: fix vulnerability and visibility, add animated webp, convenience, and optimization

https://www.hyphanet.org/freenet-hyphanet-build-15021503-fix-vulnerability-and-visibility-add-animated-webp-convenience-and-optimization.html

1502 fixed an inserter tracing vulnerability and added several features, 1503 fixes regressions in 1502.

- fix vulnerability
- reduce visibility on the network
- support animated webp and more modern HTML and CSS
- enable direct linking to Freemail’s “New Message” page
- dismiss alerts and convenience
- substantial routing optimizations
- bug fixes