sepolicy: add version_policy tool and version non-platform policy.

In order to support platform changes without simultaneous updates from
non-platform components, the platform and non-platform policies must be
split.  In order to provide a guarantee that policy written for
non-platform objects continues to provide the same access, all types
exposed to non-platform policy are versioned by converting them and the
policy using them into attributes.

This change performs that split, the subsequent versioning and also
generates a mapping file to glue the different policy components
together.

Test: Device boots and runs.
Bug: 31369363
Change-Id: Ibfd3eb077bd9b8e2ff3b2e6a0ca87e44d78b1317
diff --git a/private/platform_app.te b/private/platform_app.te
new file mode 100644
index 0000000..e478039
--- /dev/null
+++ b/private/platform_app.te
@@ -0,0 +1,4 @@
+# app_domain fallout
+tmpfs_domain(platform_app)
+# Map with PROT_EXEC.
+allow platform_app platform_app_tmpfs:file execute;