android: unbreak KO on scoped storage devices

datastorage.lua

@@ -11,7 +11,7 @@ function DataStorage:getDataDir()
     if data_dir then return data_dir end
 
     if isAndroid then
-        data_dir = android.externalStorage() .. "/koreader"
+        data_dir = android.getExternalStoragePath() .. "/koreader"
     elseif os.getenv("UBUNTU_APPLICATION_ISOLATION") then
         local app_id = os.getenv("APP_ID")
         local package_name = app_id:match("^(.-)_")

frontend/device/android/device.lua

@@ -20,7 +20,11 @@ local function getCodename()
     local api = android.app.activity.sdkVersion
     local codename = ""
 
-    if api > 27 then
+    if api > 29 then
+        codename = "R"
+    elseif api == 29 then
+        codename = "Q"
+    elseif api == 28 then
         codename = "Pie"
     elseif api == 27 or api == 26 then
         codename = "Oreo"