Fix integer's % operation; fix parsing of doubles; update co19 tests.

runtime/lib/integers.dart

Index: runtime/lib/integers.dart
===================================================================
--- runtime/lib/integers.dart	(revision 1585)
+++ runtime/lib/integers.dart	(working copy)
@@ -24,7 +24,7 @@
     return this.toDouble() / other.toDouble();
   }
   num operator %(num other) {
-    if (other == 0) {
+    if ((other is int) && (other == 0)) {
       throw const IntegerDivisionByZeroException();
     }
     return other.moduloFromInteger(this);
@@ -118,12 +118,15 @@
   }
 
   String toStringAsFixed(int fractionDigits) {
+    // Issue 460.
     throw "IntegerImplementation.toStringAsFixed not implemented";
   }
   String toStringAsExponential(int fractionDigits) {
+    // Issue 460.
     throw "IntegerImplementation.toStringAsExponential not implemented";
   }
   String toStringAsPrecision(int precision) {
+    // Issue 460.
     throw "IntegerImplementation.toStringAsPrecision not implemented";
   }
   String toRadixString(int radix) {