Makes it more obvious which parts are only used within the translation
unit, and which functions are part of the exposed interface in the
headers (and also has the benefit of allowing better
inlining/optimizing)
Passing in --sbk=, --tseckey= with -t keygen and an input BOOT0
BIS partition will now derive all keys derivable iwth the sources
in the loaded keyset, and print them to output.
