Fix many compilation warnings

app/src/main/java/eu/kanade/tachiyomi/data/backup/BackupCreateService.kt

@@ -84,9 +84,6 @@ class BackupCreateService : IntentService(NAME) {
         // Create root object
         val root = JsonObject()
 
-        // Create information object
-        val information = JsonObject()
-
         // Create manga array
         val mangaEntries = JsonArray()
 

app/src/main/java/eu/kanade/tachiyomi/data/backup/BackupRestoreService.kt

@@ -317,8 +317,8 @@ class BackupRestoreService : Service() {
                     manga
                 }
                 .filter { it.id != null }
-                .flatMap { manga ->
-                    chapterFetchObservable(source, manga, chapters)
+                .flatMap {
+                    chapterFetchObservable(source, it, chapters)
                             // Convert to the manga that contains new chapters.
                             .map { manga }
                 }

app/src/main/java/eu/kanade/tachiyomi/data/download/DownloadService.kt

@@ -122,7 +122,7 @@ class DownloadService : Service() {
                 .subscribeOn(Schedulers.io())
                 .observeOn(AndroidSchedulers.mainThread())
                 .subscribe({ state -> onNetworkStateChanged(state)
-                }, { error ->
+                }, { _ ->
                     toast(R.string.download_queue_error)
                     stopSelf()
                 })

app/src/main/java/eu/kanade/tachiyomi/data/download/Downloader.kt

@@ -287,7 +287,7 @@ class Downloader(private val context: Context, private val provider: DownloadPro
         }
 
         return pageListObservable
-                .doOnNext { pages ->
+                .doOnNext { _ ->
                     // Delete all temporary (unfinished) files
                     tmpDir.listFiles()
                             ?.filter { it.name!!.endsWith(".tmp") }
@@ -303,7 +303,7 @@ class Downloader(private val context: Context, private val provider: DownloadPro
                 // Do when page is downloaded.
                 .doOnNext { notifier.onProgressChange(download, queue) }
                 .toList()
-                .map { pages -> download }
+                .map { _ -> download }
                 // Do after download completes
                 .doOnNext { ensureSuccessfulDownload(download, tmpDir, chapterDirname) }
                 // If the page list threw, it will resume here