[PATCH] v6 for detached headers and key files

[Denis 'GNUtoo' Carikli]

Hi,

Here's a new version of this patchset.

The only change with the v5 is that I fixed the issue that Glenn
Washburn found (in the 4/6 patch, one of the grub_file_seek return
code wasn't properly checked). Thanks for finding the issue.

I also took some time to send it again because I tried to test with
the chainload with Coreboot in order to minimize the risk of 
non-booting computer, and as it took too much time (missing modules,
etc), I ended up dedicating a computer with SeaBIOS for the test.

Denis.