(and associated targets for .dvi et al), as well as man pages from .pod,
using a prefix of `# '.
This prevents a variety of build issues caused by situations such as
cvs checkouts which result in the .texinfo file being slightly newer
than the .info file, and the build process trying to unnecessarily
regenerate them, which will fail in a variety of circumstances
(build tools not available, read-only source, etc ...)
Once a better solution is found, we can switch to it.
For now, this improves things greatly and should reduce a lot of
support requests that would undoubtably appear otherwise...