If buildtoc can't open a Pod file, that's fatal, not a warning and skip.

If buildtoc can't open a Pod file, that's fatal, not a warning and skip.

The logic within the File::Find::find() callback was to attempt to open any
file, and if it failed, politely report a warning and run system ls -l on the
offending name. It's been the same since pod/buildtoc was added in December
1995 by commit cb1a09d0194fed9b ("This is patch.2b1g to perl5.002beta1.").

However the ls -l would never have worked, as it uses the full pathname
(from the top of the build tree), while File::Find::find() has changed the
current directory to the directory which it is scanning. The failure to open
"should" never happen, so if it does, it should be brought to a human's
attention instead of being glossed over.

The new approach takes less code.