[Rd] LOGNAME env var in the check code

[Gábor Csárdi]

While trying to reproduce a NOTE for

* checking for new files in some other directories ... NOTE

I noticed that the check code uses

Sys.getenv("LOGNAME")

to query the name of the current user. However on many systems this is
not set, so this is the empty string, and then no NOTE is shown. (Only
files owned by the current user generate a NOTE.)

An alternative would be to call `id -un` to query the username, or
create a file and then use `file.info()` to query its owner. Using one
of these alternatives would make this check more reproducible.

Thanks,
Gabor