Allow to select packages that conflict in case we are looking for
errors. This allows 'add --force' to install (on boot) the set of
packages with minimum conflicts.
* each package name has two sorting positions, one which causes
install_if triggers to be run, and other for bulk dependencies
* fix also inverted ordering of package installations
* the solver no longer does look-ahead locking of names
(could be possibly optimized later); instead names are now
always ordered strictly to properly detect the package names
which are unsolveable
* basic error tests added, so we can see the most likely problem
in dependencies easily
* basic code for a backtracking, forward checking dependency satisfier
* works better when there are tricky dependencies to solve
(when can't just upgrade everything to most preferred versions)
* the new code always evaluates all of 'world' constraints
(old code just does incremental updates based on heuristics)
* is probably somewhat slower than old code (probably unnoticeable
difference in most cases)
* makes easier to write support for provides and repository pinning
* test applet and a bunch of test cases added which uses the new code
* from the old feature set install_if is not yet implemented
Timo Teräs