Revert "Fix savannah bug #63567"

Commit e89c7a45eb broke deletion from archives. The reported number
of bytes read is rounded to the nearest record anyway, revert the
commit and document the fact.

Reported by Ed Santiago. See
https://bugzilla.redhat.com/show_bug.cgi?id=2230127

* doc/tar.texi: Document the fact that --totals rounds up the
number of bytes reads to the nearest record.
* src/buffer.c: Revert changes.
* tests/delete06.at: Fix expected status code and stderr.

tests/delete06.at

@@ -36,7 +36,10 @@ esac
 dd if=archive.tar of=trunc.tar bs=$size count=1 2>/dev/null
 tar --delete 'b/' -f trunc.tar
 ],
-[0],
-[],[],[],[],[gnu, pax])
+[2],
+[],
+[tar: lseek: trunc.tar: Value too large for defined data type
+tar: Exiting with failure status due to previous errors
+],[],[],[gnu, pax])
 
 AT_CLEANUP