Only handle PL_rs differently on VMS for record-oriented files.

Only handle PL_rs differently on VMS for record-oriented files.

For stream-oriented files, the effects of buffering and other
layers should be exactly as they are on other platforms. For true,
record-oriented files, though, setting $/ = \number must provide
exactly one low-level read per record.  If a read were ever to
return less than a full record (due to, for example, filling up
the perlio buffer), a subsequent read would get the *next* record,
losing whatever data remained in the partially-read record.