UrlEncode fix for input strings > 32766 limit

Initial code by @jeffthieleke-wf with my additions of null parameter
check, correct maxLength of 32766, and matching indentations per
@haacked.

Author: robertmiles3

RestSharp/Extensions/StringExtensions.cs

@@ -49,7 +49,24 @@ public static string UrlDecode(this string input)
 		/// </summary>
 		public static string UrlEncode(this string input)
 		{
-			return Uri.EscapeDataString(input);
+			const int maxLength = 32766;
+			if (input == null)
+				throw new ArgumentNullException("input");
+
+			if (input.Length <= maxLength)
+				return Uri.EscapeDataString(input);
+
+			StringBuilder sb = new StringBuilder(input.Length * 2);
+			int index = 0;
+			while (index < input.Length)
+			{
+				int length = Math.Min(input.Length - index, maxLength);
+				string subString = input.Substring(index, length);
+				sb.Append(Uri.EscapeDataString(subString));
+				index += subString.Length;
+			}
+
+			return sb.ToString();
 		}
 
 		public static string HtmlDecode(this string input)