MFV: Import atf-0.21.

MFV: Import atf-0.18.

Approved by: rpaulo (mentor)

Merge ATF 0.16 from vendor/atf/dist.

Provenance: http://code.google.com/p/kyua
Discussed with: gibbs, gnn, keramida, mdf, mlaier,
Discussed with: Garrett Cooper