bump trunk's machine version to the next series

<?xml version="1.0" encoding="utf-8"?>

<manifest

    xmlns:android="http://schemas.android.com/apk/res/android"

    android:versionCode="12045"

    android:versionCode="13000"

    android:versionName="3.512" package="com.fsck.k9"

    >

    <uses-sdk