`else if` statements are not measured as lines

[cgewecke]

(#430, #502: relevant for --matrix option)

e.g

if (a > 3)
  x = 5;
} else if (a <= 1) { // Not a line!?
  y = 7;
}

This is esp. a problem for mutation testing; changes to the second condition won't have a list of tests to run.