Clean up the makefiles a bit and make them OBJDIR-safe.
When creating a package, compute the flatsize if it is not specified
in the manifest.  Note that there is just a short leap from here to
allowing the sizes of individual files to be recorded in the manifest,
but that requires an API change.
speling ;)
Merge pull request #544 from felderado/master

simple grammer
Merge pull request #542 from dag-erling/makefiles

Clean up the makefiles a bit and make them OBJDIR-safe.
Merge pull request #543 from dag-erling/flatsize

When creating a package, compute the flatsize if it is not specified in the manifest.