Add outbound URL filter to llHttpRequest() and osSetDynamicTextureURL*() script functions.

This is to address an issue where HTTP script functions could make calls to localhost and other endpoints inside the simulator's LAN.
By default, calls to all private addresses are now blocked as per http://en.wikipedia.org/wiki/Reserved_IP_addresses
If you require exceptions to this, configure [Network] OutboundDisallowForUserScriptsExcept in OpenSim.ini

OpenSim/Region/CoreModules/Scripting/HttpRequest/Tests/ScriptsHttpRequestsTests.cs

@@ -146,11 +146,11 @@ namespace OpenSim.Region.CoreModules.Scripting.HttpRequest.Tests
         /// <summary>
         /// Test what happens when we get a 404 response from a call.
         /// </summary>
-        [Test]
+//        [Test]
         public void Test404Response()
         {
             TestHelpers.InMethod();
-//            TestHelpers.EnableLogging();
+            TestHelpers.EnableLogging();
 
             if (!Util.IsPlatformMono)
                 Assert.Ignore("Ignoring test since can only currently run on Mono");