Add empty crypto and fix user validator compilation

src/Microsoft.AspNet.Identity/Crypto.cs

@@ -0,0 +1,17 @@
+#if K10
+
+using System;
+using System.Runtime.CompilerServices;
+//using System.Security.Cryptography;
+
+namespace Microsoft.AspNet.Identity
+{
+    public class Foo
+    {
+        public Foo()
+        {
+            System.Security.Cryptography.Rfc2898DeriveBytes foo = null;
+        }
+    }
+}
+#endif

src/Microsoft.AspNet.Identity/UserValidator.cs

@@ -1,7 +1,9 @@
 using System;
 using System.Collections.Generic;
 using System.Globalization;
+#if NET45
 using System.Net.Mail;
+#endif
 using System.Text.RegularExpressions;
 using System.Threading.Tasks;
 
@@ -96,6 +98,7 @@ namespace Microsoft.AspNet.Identity
                 errors.Add(String.Format(CultureInfo.CurrentCulture, Resources.PropertyTooShort, "Email"));
                 return;
             }
+#if NET45
             try
             {
                 var m = new MailAddress(email);
@@ -105,6 +108,7 @@ namespace Microsoft.AspNet.Identity
                 errors.Add(String.Format(CultureInfo.CurrentCulture, Resources.InvalidEmail, email));
                 return;
             }
+#endif
             var owner = await Manager.FindByEmail(email);
             if (owner != null && !EqualityComparer<TKey>.Default.Equals(owner.Id, user.Id))
             {