A new approach to SEF URLsDoing some benchmarks, I found pretty devastating results for the performance of the output buffer rewrite that is needed to rewrite all URLs into a nice looking (or so-called "SEO friendly") format. The time it needs obviously depends on 2 factors:Number of URLs to rewriteThe size of the bufferIt was acceptable for smaller pages (like the board index), but totally disappointing for larger pages, especially long topic views. Up to 130ms for the rewriting of more than 300 URLs in the buffer is totally insane when the actual page generation took only about 30ms. That could easily kill a large board under heavy load...Reducing the number of URLs to rewrite will obviously help and we don't really need pretty URLs for everything. All the links that search engines will never see (like the buttons for posting, quoting, replying or links that only appear for registered users) can be left in the standard URL format. Furthermore, creating the links already in their prettified form helps again and is a good opportunity to clean up the messy and repetitive URL generation throughout the code, replacing it with common functions that can generate URLs for topics, profiles, boards and other things.Such URLs are already in the pretty format and this will save a lot of time in the buffer rewriting process.Commit ID: cb5bded4e15c15750854806285eb790fbe6c8920, 22 changed files with 380 additions and 318 deletions.Commit ID: aaf1b40a384eb00933891f6e92e354a52afc8324, 11 changed files with 157 additions and 52 deletions.Fixed a serious issue with SEF URLs leading to noindex tags on topic and message index pages.Improved UI for editing board news items.Make SimpleSEF redirects from standard to prettyfied URLs optionalImplemented generic URL generators for topic, board and profile URLsOnly rewrite necessary URLs in the output bufferWith the new URL generation and lightweight buffer rewriting that only looks at a few URLs that could not be generated during page build up (one example would be URLs from BBCodes) the performance impact for SEO URls is now minimal. On average, 5-10ms are spent on buffer rewriting for a long page and for most others, the numbers are much lower on my testing system (the actual numbers appear in the bottom right corner of every page). I think, that's acceptable. It should be clear that pretty URLs will always come with a price tag attached, but it doesn't have to be a hefty one.