This avoids turning a prerequisite search into a massacre of, guessed,
O(sqrt(2^requisites)).
- gobble.c (gobble_buf, compact_pkg): if a package being added has the same
version as an existing package with the same name, merge them and keep
only one
With the reduction of search depth, "prereq abiword" takes about 3 minutes
on my PC. (Obviously, this can still be improved.)
- gobble.c (gobble_buf): if pkg->id->value is NULL, just it as such
- prereq.c (push): abort if trying to consider a package already considered
or installed
- prereq.c (conflicts): before being satisfied with using an installed
package, make sure it really satisfies the requirement
- prereq.c (conflicts): abort if an installed package conflicts
- prereq.c (conflicts): added some debugging output (temporary)
- prereq.c (conflicts): cut the search if we can't do better than a
previous match
