Fix Uri when a colon ':' is not followed by a port number

* System/Uri.cs: Fix parsing the port/host when a ':' is present without
a port number on non-file:// URI

* Test/System/UriTest2.cs: Add test cases where an URI contains a ':'
but is not followed by a port number

mcs/class/System/System/Uri.cs

@@ -1528,10 +1528,14 @@ private string ParseNoExceptions (UriKind kind, string uriString)
 						port = GetDefaultPort (scheme);
 					}
 				}
-			} else {
-				if (port == -1) {
+			} else if (!IsFile) {
+				// if no port is specified by a colon ':' is present then we must ignore it
+				// since it would be part of the host name and, as such, would be invalid
+				if (pos == endpos - 1)
+					endpos--;
+
+				if (port == -1)
 					port = GetDefaultPort (scheme);
-				}
 			}
 
 			// 4 authority

mcs/class/System/Test/System/UriTest2.cs

@@ -879,5 +879,21 @@ public void PathReduction_2e ()
 			Assert.AreEqual ("/", uri.Segments [0], "Segments [0]");
 			Assert.AreEqual ("file", uri.Segments [1], "Segments [1]");
 		}
+
+		[Test]
+		public void ColonButNoPort ()
+		{
+			Uri uri = new Uri ("http://host:");
+			Assert.AreEqual ("http", uri.Scheme, "1.Scheme");
+			Assert.AreEqual ("host", uri.Host, "1.Host");
+			Assert.AreEqual (80, uri.Port, "1.Port");
+			Assert.IsTrue (uri.IsDefaultPort, "1.IsDefaultPort");
+
+			uri = new Uri ("ftp://host:/dir/file");
+			Assert.AreEqual ("ftp", uri.Scheme, "2.Scheme");
+			Assert.AreEqual ("host", uri.Host, "2.Host");
+			Assert.AreEqual (21, uri.Port, "2.Port");
+			Assert.IsTrue (uri.IsDefaultPort, "2.IsDefaultPort");
+		}
 	}
 }