FBE for Pixel 2

Includes various minor fixes for building in Android 8 trees with r23+ tag

Update FBE extended header in libtar to version 2 and include the entire
ext4_encryption_policy structure now after translating the policy.

See this post for more details:
https://plus.google.com/u/1/+DeesTroy/posts/i33ygUi7tiu

Change-Id: I2af981e51f459b17fcd895fb8c2d3f6c8200e24b

crypto/ext4crypt/Ext4Crypt.cpp

@@ -41,8 +41,16 @@
 
 #include <private/android_filesystem_config.h>
 
+#ifdef HAVE_SYNTH_PWD_SUPPORT
+#include <ext4_utils/ext4_crypt.h>
+#else
 #include "ext4_crypt.h"
+#endif
+#ifndef HAVE_LIBKEYUTILS
 #include "key_control.h"
+#else
+#include <keyutils.h>
+#endif
 
 #include <hardware/gatekeeper.h>
 #include "HashPassword.h"