Fixed logic for trimming trailing blank lines for the DKIM relaxed bo…

…dy algorithm

Fixes issue #187

MimeKit/Cryptography/DkimRelaxedBodyFilter.cs

@@ -89,7 +89,7 @@ unsafe int Filter (byte* inbuf, int length, byte* outbuf)
 
 					if ((*inptr).IsBlank ()) {
 						LastWasNewLine = false;
-						IsEmptyLine = false;
+						//IsEmptyLine = false;
 						lwsp = true;
 					} else {
 						if (lwsp) {

UnitTests/DkimRelaxedBodyFilterTests.cs

@@ -41,11 +41,29 @@ namespace UnitTests {
 	[TestFixture]
 	public class DkimRelaxedBodyFilterTests
 	{
+		// Disabled because it conflicts with TestTrimmingEmptyLines()
+//		[Test]
+//		public void TestWhiteSpaceBeforeNewLine ()
+//		{
+//			const string text = "This is a test of the relaxed body filter   \n   \n";
+//			const string expected = "This is a test of the relaxed body filter\n\n";
+//			var input = Encoding.ASCII.GetBytes (text);
+//			var filter = new DkimRelaxedBodyFilter ();
+//			int outputIndex, outputLength;
+//			byte[] output;
+//			string actual;
+//
+//			output = filter.Flush (input, 0, input.Length, out outputIndex, out outputLength);
+//			actual = Encoding.ASCII.GetString (output, outputIndex, outputLength);
+//
+//			Assert.AreEqual (expected, actual);
+//		}
+
 		[Test]
-		public void TestWhiteSpaceBeforeNewLine ()
+		public void TestTrimmingEmptyLines ()
 		{
-			const string text = "This is a test of the relaxed body filter   \n   \n";
-			const string expected = "This is a test of the relaxed body filter\n\n";
+			const string text = "Hello!\r\n  \r\n\r\n";
+			const string expected = "Hello!\r\n";
 			var input = Encoding.ASCII.GetBytes (text);
 			var filter = new DkimRelaxedBodyFilter ();
 			int outputIndex, outputLength;