Instead of the dependency oriented logic, switch to print them
for each package or name needed. Might give a bit more readable
errors now. There's still few corner cases that proper error is
not output, which are cought by the test cases.
* 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
Timo Teräs