Android: Add content provider support to File::IOFile

Taking the hit now to prepare us for when Google Play will
force us to use scoped storage...

Source/Android/app/src/main/java/org/dolphinemu/dolphinemu/utils/ContentHandler.java

@@ -0,0 +1,23 @@
+package org.dolphinemu.dolphinemu.utils;
+
+import android.net.Uri;
+
+import org.dolphinemu.dolphinemu.DolphinApplication;
+
+import java.io.FileNotFoundException;
+
+public class ContentHandler
+{
+  public static int openFd(String uri, String mode)
+  {
+    try
+    {
+      return DolphinApplication.getAppContext().getContentResolver()
+              .openFileDescriptor(Uri.parse(uri), mode).detachFd();
+    }
+    catch (FileNotFoundException | NullPointerException e)
+    {
+      return -1;
+    }
+  }
+}