[Dillo-dev] Dicache work

Hi there, There're three new dicache patches in the repo. These have beeen tested/checked with valgrind and gcc's address sanitizer. Given the last memory usage reports, and a very necessary cleanup that was pending for a long time, this patch set tries to tackle the issue. There's also some decompressed image caching enabled (read the verbose changelog) that will make dillo feel faster. Please test and send feedback. BTW, I found ways to crash dillo without the patches and wonder whether some of you also experimented image-related crashes. -- Cheers Jorge.-