- think about consolidating the -A/-U/-S options into one smart
  install operation
- replaces code doesn't run with -U or -A
- when performing replaces, pacman should not remove old packages until
  the conflict checks are passed
- handle version comparators in makepkg dep resolution (eg, glibc>=2.2.5)
- add post_remove, pre_install, pre_upgrade functions to scriptlets
- check $PACCONF env var
- add a --pretend option
