Fix create-manifest.sh for raw pkg-message files to match porter's handbook.

[mandree]

Summary

The porter's handbook in section 9.1 (as of r54044) proudly proclaims

pkg-message supports two formats:

raw

A regular plain text file. Its message is always displayed, on install, and on upgrade.

But that's untrue. Fix create-manifest.sh so that freshly created packages live up to that standard.

[mandree]

I should mention that this was tested successfully on sysutils/e2fsprogs.

[mat]

In this case, the documentation is wrong, I will fix the documentation.