ToString methods of ulong/UInt64 and long/Int64 are not returning the correct values

[MatthiasJentsch]

Details about Problem

nanoFramework area: nanoCLR preview 791

Worked before? No

Detailed repro steps so we can see the same problem

using System;

namespace NFApp1
{
	public class Program
	{
		public static void Main()
		{
			// Should output "12345678998765432101" but outputs "2691296549"
			Console.WriteLine(((ulong)12345678998765432101).ToString());
			// Should output "AB54A9A3A069ED25" but outputs "00000000A069ED25"
			Console.WriteLine(((ulong)12345678998765432101).ToString("X16"));
			// Should output "-1234567899876543210" but outputs "1019360534"
			Console.WriteLine(((long)-1234567899876543210).ToString());
			// Should output "EEDDEF093CC23516" but outputs "3CC2351600000000"
			Console.WriteLine(((long)-1234567899876543210).ToString("X16"));
		}
	}
}