MFH: r447501 r447660
www/firefox: update to 55.0.1
This is the last release to support RUST=off. Later versions
remove non-Rust codepaths e.g., via encoding_rs.
Changes: https://www.mozilla.org/firefox/55.0.1/releasenotes/
PR: 216541 219963
Security: 555b244e-6b20-4546-851f-d8eb7d6c1ffa
Approved by: ports-secteam (zi)