UEFI related headers were copied from edk2.
A new build option "MK_LOADER_EFI_SECUREBOOT" was added to allow the loading of trusted anchors from UEFI.
Certificate revocation support is also introduced.
The forbidden certificates are loaded from dbx variable.
Verification fails in two cases:
1. There is a direct match between cert in dbx and the one in the chain.
2. The CA used to sign the chain is found in dbx.
One can also insert a hash of TBS section of a certificate into dbx.
In this case verifications fails only if a direct match with a certificate in chain is found.
It depends on @sjg patches: