CVS commit by mornfall: Reduce time complexity of agent processing pass significantly. Achieved by changing the deque that served as an agent queue to std::list (no idea why it was deque before... no random access operations were done, unlike many middle-removals) and adding a random-access cache indexed by package id and agent type (want/unwant). The overall speedup is about factor 14 (full init of extended state takes < 5 seconds (was > 60), single package change about 0.15 second... WHEEE!).
M +25 -9 pkgcache.cpp 1.25 M +10 -4 pkgcache.h 1.21
