Handle bad PORTAGE_BINHOST gracefully (bug 502288)
DEVELOPING: Mention that tab stop should be 4
Clean up bad PORTAGE_BINHOST handling

Suggested-by: Arfrever Frehtes Taifersar Arahesis <Arfrever@Apache.Org>
Reviewed-by: Arfrever Frehtes Taifersar Arahesis <Arfrever@Apache.Org>
Add a test case for --newuse, --changed-use, and --binpkg-respect-use.

Change-Id: I201e468c6e7cda6aa961371ad9ddc10cfab04bc7