Moved LQ to XCache

I just moved part of the LQ infrastructure (the main site) from APC to XCache. I haven't necessarily been unhappy with APC, but I've seen a lot about XCache recently so I figured I'd check it out. We have some other performance improvements planned for LQ in the near future, but every bit helps. If you notice any difference, let me know. LQ gets a good amount of traffic and we're planning for solid growth this year, so ensuring the infrastructure is scalable and performant is critical for us. If there's a big difference either way, I'll report back here. Next up is to see if Xdebug works with XCache enabled (last time I checked, it didn't work with APC enabled).
–jeremy