Odroid XU3 support

Add defconfigs for seL4 test.
Merge pull request #4 from pchubb/master

Odroid XU3 support
trivial: Remove unused variable.

Found by Goanna.
Fix: Avoid dereferencing a possibly NULL pointer.

Found by Goanna
Clarify some intentionally unreachable code.
Merge pull request #5 from mfernandez/goanna

Miscellaneous fixes based on errors found by Goanna.