[Nmh-workers] filenames in error messages

[pmaydell]

Here's a real bikeshed-painting question: what format should we be using
for filenames in error messages?

I notice that in sbr/context_read.c we have all of the following:

"`%s' specified by your MH environment variable is not a normal file"
"Your %s file does not contain a path entry."
"unable to access MH-directory \"%s\""

which seems rather inconsistent -- but what should we be tidying up to?
I think the most common is probably unadorned %s...

-- PMM