webapp: Use IP address, rather than localhost

since some systems may have configuration problems or other issues that
prevent web browsers from connecting to the right localhost IP for the
webapp.

Tested on both ipv4 and ipv6 localhost. Url for the latter looks like:
http://[::1]:50676

Assistant/Threads/WebApp.hs

@@ -35,7 +35,7 @@ import Git
 
 import Yesod
 import Yesod.Static
-import Network.Socket (PortNumber)
+import Network.Socket (SockAddr)
 import Data.Text (pack, unpack)
 
 thisThread :: String
@@ -67,14 +67,14 @@ webAppThread assistantdata urlrenderer noannex postfirstrun onstartup = thread $
 		( return $ httpDebugLogger app
 		, return app
 		)
-	runWebApp app' $ \port -> if noannex
+	runWebApp app' $ \addr -> if noannex
 		then withTempFile "webapp.html" $ \tmpfile _ ->
-			go port webapp tmpfile Nothing
+			go addr webapp tmpfile Nothing
 		else do
 			let st = threadState assistantdata
 			htmlshim <- runThreadState st $ fromRepo gitAnnexHtmlShim
 			urlfile <- runThreadState st $ fromRepo gitAnnexUrlFile
-			go port webapp htmlshim (Just urlfile)
+			go addr webapp htmlshim (Just urlfile)
   where
 	thread = NamedThread thisThread
 	getreldir
@@ -82,13 +82,13 @@ webAppThread assistantdata urlrenderer noannex postfirstrun onstartup = thread $
 		| otherwise = Just <$>
 			(relHome =<< absPath
 				=<< runThreadState (threadState assistantdata) (fromRepo repoPath))
-	go port webapp htmlshim urlfile = do
-		let url = myUrl webapp port
+	go addr webapp htmlshim urlfile = do
+		let url = myUrl webapp addr
 		maybe noop (`writeFileProtected` url) urlfile
 		writeHtmlShim "Starting webapp..." url htmlshim
 		maybe noop (\a -> a url htmlshim) onstartup
 
-myUrl :: WebApp -> PortNumber -> Url
-myUrl webapp port = unpack $ yesodRender webapp urlbase HomeR []
+myUrl :: WebApp -> SockAddr -> Url
+myUrl webapp addr = unpack $ yesodRender webapp urlbase HomeR []
   where
-	urlbase = pack $ "http://localhost:" ++ show port
+	urlbase = pack $ "http://" ++ show addr