android: Fix app icon on Android versions < 5.0

XML resources are apparently not supported there.  Moving the icon to
the mipmap folders should fix that.  Aliases are defined for the icons on
Android < 8.0.

src/frontends/android/app/src/main/java/org/strongswan/android/ui/MainActivity.java

@@ -66,7 +66,7 @@ public class MainActivity extends AppCompatActivity implements OnVpnProfileSelec
 		ActionBar bar = getSupportActionBar();
 		bar.setDisplayShowHomeEnabled(true);
 		bar.setDisplayShowTitleEnabled(false);
-		bar.setIcon(R.drawable.ic_launcher);
+		bar.setIcon(R.mipmap.ic_app);
 
 		/* load CA certificates in a background task */
 		new LoadCertificatesTask().executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);

src/frontends/android/app/src/main/java/org/strongswan/android/ui/TrustedCertificateImportActivity.java

@@ -202,7 +202,7 @@ public class TrustedCertificateImportActivity extends AppCompatActivity
 			certificate = (X509Certificate)getArguments().getSerializable(VpnProfileDataSource.KEY_CERTIFICATE);
 
 			return new AlertDialog.Builder(getActivity())
-				.setIcon(R.drawable.ic_launcher)
+				.setIcon(R.mipmap.ic_app)
 				.setTitle(R.string.import_certificate)
 				.setMessage(certificate.getSubjectDN().toString())
 				.setPositiveButton(R.string.import_certificate, new DialogInterface.OnClickListener()

src/frontends/android/app/src/main/res/mipmap-anydpi/ic_shortcut.xml

@@ -1,17 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-<!--
-    Copyright (C) 2018 Tobias Brunner
-    HSR Hochschule fuer Technik Rapperswil
-
-    This program 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 2 of the License, or (at your
-    option) any later version.  See <http://www.fsf.org/copyleft/gpl.txt>.
-
-    This program 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.
--->
-<inset xmlns:android="http://schemas.android.com/apk/res/android"
-    android:drawable="@drawable/ic_launcher" />

src/frontends/android/app/src/main/res/values/mipmaps.xml

@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <!--
-    Copyright (C) 2018 Tobias Brunner
+    Copyright (C) 2020 Tobias Brunner
     HSR Hochschule fuer Technik Rapperswil
 
     This program is free software; you can redistribute it and/or modify it
@@ -13,5 +13,7 @@
     or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
     for more details.
 -->
-<inset xmlns:android="http://schemas.android.com/apk/res/android"
-    android:drawable="@drawable/ic_launcher" />
+<resources>
+    <mipmap name="ic_launcher">@mipmap/ic_app</mipmap>
+    <mipmap name="ic_shortcut">@mipmap/ic_app</mipmap>
+</resources>