Added/improved charset mapping

app/src/main/java/eu/faircode/email/UnknownCharsetProvider.java

@@ -1,48 +0,0 @@
-package eu.faircode.email;
-
-/*
-    This file is part of FairEmail.
-
-    FairEmail is free software: you can redistribute it and/or modify
-    it under the terms of the GNU General Public License as published by
-    the Free Software Foundation, either version 3 of the License, or
-    (at your option) any later version.
-
-    FairEmail is distributed in the hope that it will be useful,
-    but WITHOUT ANY WARRANTY; without even the implied warranty of
-    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-    GNU General Public License for more details.
-
-    You should have received a copy of the GNU General Public License
-    along with FairEmail.  If not, see <http://www.gnu.org/licenses/>.
-
-    Copyright 2018-2020 by Marcel Bokhorst (M66B)
-*/
-
-import android.text.TextUtils;
-
-import java.nio.charset.Charset;
-import java.nio.charset.StandardCharsets;
-import java.nio.charset.spi.CharsetProvider;
-import java.util.Collections;
-import java.util.Iterator;
-
-public class UnknownCharsetProvider extends CharsetProvider {
-    @Override
-    public Iterator<Charset> charsets() {
-        return Collections.emptyIterator();
-    }
-
-    @Override
-    public Charset charsetForName(String name) {
-        // x-binaryenc
-        // UseInqueCodePage
-        // none
-        // unknown-8bit
-        // X-UNKNOWN
-        // https://javaee.github.io/javamail/FAQ#unsupen
-        if (!TextUtils.isEmpty(name))
-            Log.e("Unknown charset=" + name);
-        return StandardCharsets.US_ASCII;
-    }
-}