More performance changes: - I've found a stupid bug that prevented some unnecessary info from being deleted from memory, so dpb's memory consumption when running a fetch engine (default) is somewhat lower. - some extra processes are removed: there's no longer a checksum process if all the distfiles have cached values, prepare and show-prepare-results have been folded together. - "small" ports (stuff that run <2 mn by default) just go directly to build/package without extra steps that run through patch/configure/fake... less extra processes, should be faster.
- a bit of analysis with NYTProf showed a few inefficiencies, mostly monkey-business with constructing fullpkgpaths again and again. I expect that LISTING is now about as fast as it can be...
