Add markup to prevent comparing system-specific details in tests

[warnes]

Prof Brian Ripley ripley@stats.ox.ac.uk
date: | Dec 26, 2019, 3:22 AM
subject: | CRAN package SASxport

See https://cran.r-project.org/web/checks/check_results_SASxport.html .

Not only is your reference output different in many ways from the
current output, it captures OS-specific and session-specific names like

Filename: /Users/gwarnes/Google Drive/src/SASxport.Rcheck/SASxport/extdata/Alfalfa.xpt

Filename: /var/folders/gc/c3c2p5_d4td159rblkqbp4s1xjhdh_/T//RtmpcNRdhA/file34e64ef05fbb.dat

Please correct ASAP once CRAN submissions re-opens on Jan 6 and before
Jan 15 to safely retain the package on CRAN.

If it is actually useful to record these filenames,

## IGNORE_RDIFF_BEGIN
## IGNORE_RDIFF_END

markup can be used to skip comparing them.

[warnes]

The offending output lines are a (useful!) part of the output of print.summary.lookup.xport.

I suppose the code could be modified to check if the code is being run under R CMD check, and omit the filename...