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.

Messages/Concurrent.hs

@@ -14,7 +14,6 @@ import Types
 import Types.Messages
 import qualified Annex
 
-#ifdef WITH_CONCURRENTOUTPUT
 import Common
 import qualified System.Console.Concurrent as Console
 import qualified System.Console.Regions as Regions
@@ -23,7 +22,6 @@ import qualified Data.Text as T
 #ifndef mingw32_HOST_OS
 import GHC.IO.Encoding
 #endif
-#endif
 
 {- Outputs a message in a concurrency safe way.
  -
@@ -33,15 +31,10 @@ import GHC.IO.Encoding
  - instead.
  -}
 concurrentMessage :: MessageState -> Bool -> String -> Annex () -> Annex ()
-#ifdef WITH_CONCURRENTOUTPUT
 concurrentMessage s iserror msg fallback 
 	| concurrentOutputEnabled s =
 		go =<< consoleRegion <$> Annex.getState Annex.output
-#else
-concurrentMessage _s _iserror _msg fallback 
-#endif
 	| otherwise = fallback
-#ifdef WITH_CONCURRENTOUTPUT
   where
 	go Nothing
 		| iserror = liftIO $ Console.errorConcurrent msg
@@ -58,7 +51,6 @@ concurrentMessage _s _iserror _msg fallback
 			rl <- takeTMVar Regions.regionList
 			putTMVar Regions.regionList
 				(if r `elem` rl then rl else r:rl)
-#endif
 
 {- Runs an action in its own dedicated region of the console.
  -
@@ -70,7 +62,6 @@ concurrentMessage _s _iserror _msg fallback
  - complete.
  -}
 inOwnConsoleRegion :: MessageState -> Annex a -> Annex a
-#ifdef WITH_CONCURRENTOUTPUT
 inOwnConsoleRegion s a
 	| concurrentOutputEnabled s = do
 		r <- mkregion
@@ -85,11 +76,7 @@ inOwnConsoleRegion s a
 			Right ret -> do
 				rmregion r
 				return ret
-#else
-inOwnConsoleRegion _s a
-#endif
 	| otherwise = a
-#ifdef WITH_CONCURRENTOUTPUT
   where
 	-- The region is allocated here, but not displayed until 
 	-- a message is added to it. This avoids unnecessary screen
@@ -108,10 +95,8 @@ inOwnConsoleRegion _s a
 			unless (T.null t) $
 				Console.bufferOutputSTM h t
 			Regions.closeConsoleRegion r
-#endif
 
 {- The progress region is displayed inline with the current console region. -}
-#ifdef WITH_CONCURRENTOUTPUT
 withProgressRegion :: (Regions.ConsoleRegion -> Annex a) -> Annex a
 withProgressRegion a = do
 	parent <- consoleRegion <$> Annex.getState Annex.output
@@ -119,14 +104,12 @@ withProgressRegion a = do
 
 instance Regions.LiftRegion Annex where
 	liftRegion = liftIO . atomically
-#endif
 
 {- The concurrent-output library uses Text, which bypasses the normal use
  - of the fileSystemEncoding to roundtrip invalid characters, when in a
  - non-unicode locale. Work around that problem by avoiding using
  - concurrent output when not in a unicode locale. -}
 concurrentOutputSupported :: IO Bool
-#ifdef WITH_CONCURRENTOUTPUT
 #ifndef mingw32_HOST_OS
 concurrentOutputSupported = do
 	enc <- getLocaleEncoding
@@ -134,9 +117,6 @@ concurrentOutputSupported = do
 #else
 concurrentOutputSupported = return True -- Windows is always unicode
 #endif
-#else
-concurrentOutputSupported = return False
-#endif
 
 {- Hide any currently displayed console regions while running the action,
  - so that the action can use the console itself.
@@ -144,7 +124,6 @@ concurrentOutputSupported = return False
  - the regions will not be hidden, but the action still runs, garbling the
  - display. -}
 hideRegionsWhile :: Annex a -> Annex a
-#ifdef WITH_CONCURRENTOUTPUT
 #if MIN_VERSION_concurrent_output(1,9,0)
 hideRegionsWhile a = bracketIO setup cleanup go
   where
@@ -156,6 +135,3 @@ hideRegionsWhile a = bracketIO setup cleanup go
 #else
 hideRegionsWhile = id
 #endif
-#else
-hideRegionsWhile = id
-#endif