Build download requests from indexer implementation

(cherry picked from commit a0b08f6c6f106d92cdb12fbb959dd2605c22fe6a)

src/NzbDrone.Core/Indexers/HttpIndexerBase.cs

@@ -68,6 +68,11 @@ namespace NzbDrone.Core.Indexers
             return FetchReleases(g => g.GetSearchRequests(searchCriteria));
         }
 
+        public override HttpRequest GetDownloadRequest(string link)
+        {
+            return new HttpRequest(link);
+        }
+
         protected virtual IList<ReleaseInfo> FetchReleases(Func<IIndexerRequestGenerator, IndexerPageableRequestChain> pageableRequestChainSelector, bool isRecent = false)
         {
             var releases = new List<ReleaseInfo>();