pkgset: deadcode, fix some false-negatives

pkgset: deadcode, eliminate some false positives

tree: print line numbers and where things were printed

pkgset: add deadcode

Add initial deadcode support.

README: special section for binary size

weight-diff: add cumulative delta

weight-diff: add aliases support

pkgset: calculate DisjointSources correctly

We need to walk all the dependencies to correctly find the actual
import counts.

Fixes #82

all: remove Repo information from package

Finding out correct repository information is very slow,
so we'll remove it to speed up the general workflow.

mod: bump golang.org/x/{mod,tools}