[vulkan] Integrate with HostConnection

bug: 111137294

This pushes vulkan components downward so that we can reuse
HostConnection and the general infrastructure around it (incl. DMA) when
running Vulkan.

This has benefits, like being able to interoperate easily with
renderControl and gralloc, and not having to create qemu pipe (or some
other transport) ourselves.

- Move VulkanStream to vulkan_enc
- Move cereal as a dependency of vulkan_enc

Note that this makes VulkanStream into a class that doesnt do any real
writing or reading, but that's fine since this is an intermediate state
and we'll hook it up to IOStream later on.

Change-Id: I7dce6798f1490f7a5874da3a4213d7b5bdf71f06
diff --git a/system/vulkan_enc/VkEncoder.cpp b/system/vulkan_enc/VkEncoder.cpp
new file mode 100644
index 0000000..d266b6b
--- /dev/null
+++ b/system/vulkan_enc/VkEncoder.cpp
@@ -0,0 +1,16 @@
+// Copyright (C) 2018 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// TODO
+void placeholder() { }