removed the old Android app

Running git-annex linux builds in termux seems to work well enough that the
only reason to keep the Android app would be to support Android 4-5, which
the old Android app supported, and which I don't know if the termux method
works on (although I see no reason why it would not).
According to [1], Android 4-5 remains on around 29% of devices, down from
51% one year ago.

[1] https://www.statista.com/statistics/271774/share-of-android-platforms-on-mobile-devices-with-android-os/

This is a rather large commit, but mostly very straightfoward removal of
android ifdefs and patches and associated cruft.

Also, removed support for building with very old ghc < 8.0.1, and with
yesod < 1.4.3, and without concurrent-output, which were only being used
by the cross build.

Some documentation specific to the Android app (screenshots etc) needs
to be updated still.

This commit was sponsored by Brett Eisenberg on Patreon.

Utility/WebApp.hs

@@ -30,9 +30,6 @@ import Blaze.ByteString.Builder.Char.Utf8 (fromText)
 import Blaze.ByteString.Builder (Builder)
 import Control.Arrow ((***))
 import Control.Concurrent
-#ifdef __ANDROID__
-import Data.Endian
-#endif
 
 localhost :: HostName
 localhost = "localhost"
@@ -42,11 +39,6 @@ browserProc :: String -> CreateProcess
 #ifdef darwin_HOST_OS
 browserProc url = proc "open" [url]
 #else
-#ifdef __ANDROID__
--- Warning: The `am` command does not work very reliably on Android.
-browserProc url = proc "am"
-	["start", "-a", "android.intent.action.VIEW", "-d", url]
-#else
 #ifdef mingw32_HOST_OS
 -- Warning: On Windows, no quoting or escaping of the url seems possible,
 -- so spaces in it will cause problems. One approach is to make the url
@@ -57,7 +49,6 @@ browserProc url = proc "cmd" ["/c start " ++ url]
 browserProc url = proc "xdg-open" [url]
 #endif
 #endif
-#endif
 
 {- Binds to a socket on localhost, or possibly a different specified
  - hostname or address, and runs a webapp on it.
@@ -69,19 +60,11 @@ runWebApp :: Maybe TLSSettings -> Maybe HostName -> Wai.Application -> (SockAddr
 runWebApp tlssettings h app observer = withSocketsDo $ do
 	sock <- getSocket h
 	void $ forkIO $ go webAppSettings sock app	
-	sockaddr <- fixSockAddr <$> getSocketName sock
+	sockaddr <- getSocketName sock
 	observer sockaddr
   where
 	go = (maybe runSettingsSocket (\ts -> runTLSSocket ts) tlssettings)
 
-fixSockAddr :: SockAddr -> SockAddr
-#ifdef __ANDROID__
-{- On Android, the port is currently incorrectly returned in network
- - byte order, which is wrong on little endian systems. -}
-fixSockAddr (SockAddrInet (PortNum port) addr) = SockAddrInet (PortNum $ swapEndian port) addr
-#endif
-fixSockAddr addr = addr
-
 -- disable buggy sloworis attack prevention code
 webAppSettings :: Settings
 webAppSettings = setTimeout halfhour defaultSettings