list.sh: add not-built and has-been-built support.
Add 'combo-list' script.

This script combines lists generated by list.sh.
Add 'build-all' and 'do-build' scripts.

'do-build' goes through a generated package list with a specified sort
           and builds each package.
'build-all' spawns a few instances of the 'do-build' script in tmux with
				different sorts. The builders conflict with each other
				sometimes, but it doesn't seem to be too much of an issue.