New mod_pagespeed: cache advances, progressive JPEGs

Mod_pagespeed 1.2 introduces enhancements aimed at improving website performance through better caching and optimization techniques. The new canonicalize_javascript_libraries feature allows sites to replace local JavaScript libraries with hosted versions from ajax.googleapis.com, reducing redundant downloads and improving load times by utilizing cached versions. Additionally, the insert_dns_prefetch filter enables faster DNS resolution by pre-resolving DNS entries for critical assets, which can significantly cut down page load times. The update also includes the ability to optimize resources from external servers not running mod_pagespeed and introduces progressive JPEG conversion as a core filter to enhance image loading and reduce file sizes. These advancements are designed to streamline the browsing experience by leveraging shared resources and minimizing unnecessary data transfer, ultimately contributing to faster web performance.