New IC/TS attribute: "one_error_per_file"

When set to nonzero, only ONE "Invalid file" or "Could not open file"
error message will be issued for each broken file.  Of course, calls that
fail will still return false, they just will have empty error messages.
This turns out to be helpful if you have an app that might make millions
of calls before it discovers a problem, and happens to be echoing non-empty
error messages.  The default is 0 (the old behavior; an error message every time).