Changes to allow user-signed kernels to be generated.

Make vbutil_keyblock handle unsigned blocks. Also enable --unpack option and
add tests for it.

Modify vbutil_kernel to allow unsigned keyblocks, correct usage message,
and fix the --debug option which was somehow disabled.

Update load_kernel_test to accept /dev/null for the public key, to test
non-signed kernel keyblocks.

Review URL:
10 files changed