- didn't actually check for non-whitespace garbage after having
     read 2 numbers per line
   - this catches mistakes like "12341 0\n134134 343\n" type files,
     where the newline was printed out explicitly [yes, I did that,so...]
   - fixes #762
Original: 3fd351f7d345f405a3cc6e5d7201bc57d61c3062