Fix for #266

-Extra: Added the appropriate images to drawable folder from Android SDK
source, can be used as alternative if required.

OpenPGP-Keychain/src/main/java/org/sufficientlysecure/keychain/ui/dialog/DeleteFileDialogFragment.java

@@ -61,7 +61,8 @@ public class DeleteFileDialogFragment extends DialogFragment {
 
         AlertDialog.Builder alert = new AlertDialog.Builder(activity);
 
-        alert.setIcon(android.R.drawable.ic_dialog_alert);
+
+        alert.setIconAttribute(android.R.attr.alertDialogIcon);
         alert.setTitle(R.string.warning);
         alert.setMessage(this.getString(R.string.file_delete_confirmation, deleteFile));
 

OpenPGP-Keychain/src/main/java/org/sufficientlysecure/keychain/ui/dialog/DeleteKeyDialogFragment.java

@@ -100,7 +100,7 @@ public class DeleteKeyDialogFragment extends DialogFragment {
             builder.setMessage(R.string.key_deletion_confirmation_multi);
         }
 
-        builder.setIcon(android.R.drawable.ic_dialog_alert);
+        builder.setIconAttribute(android.R.attr.alertDialogIcon);
         builder.setPositiveButton(R.string.btn_delete, new DialogInterface.OnClickListener() {
 
             @Override