Add test for too-large negative integer (and remove todo for this test)
diff --git a/src/qcbor_decode.c b/src/qcbor_decode.c
index c35a29d..a5d81ac 100644
--- a/src/qcbor_decode.c
+++ b/src/qcbor_decode.c
@@ -487,7 +487,7 @@
 
       } else {
          // C can't represent a negative integer in this range
-         // so it is an error.  todo -- test this condition
+         // so it is an error.
          nReturn = QCBOR_ERR_INT_OVERFLOW;
       }
    }