Merged from trunk 5320:5333

Merged from trunk 5320:5333

For bug #158503, allow --nodeps to override blockers.

Increase cache hits in portdbapi.xmatch().

Use a separate digraph to store parent/child relationships (PDEPEND
relationships are not reversed) so that relationship is always known in
case a slot collision occurs.

New elog modules for dismerging messages into a single file/mail
(genone)

Make binarytree.move_ent() properly update PF.

For bug #158558, fix broken ebuild rename logic in vardbapi.move_ent().

For bug #158558, make the unmerge phase do automatic cleanup for broken
vardbapi.move_ent() in portage versions before 2.1.2.

Fix an import statement typo.

For bug #158608, don't attempt to use distlocks when it's detected that
the filesystem is readonly (unless "skiprocheck" is in FEATURES for some
strange reason).

Add missing newlines to the warning message that's printed when the user
has distlocks enabled together with skiprocheck and the filesystem is
readonly.

Give the user some advice whenever an invalid dependency string is
encountered.

Fix the invalid dependency message so there's no confusion about which
package has the problem.

svn path=/main/branches/prefix/; revision=5334