Create package msgqueue.

Create package msgqueue, define primitives to be used for message
queues, and add a msgqueue.Registry to IPCNamespace.

Updates #135

pkg/sentry/kernel/msgqueue/BUILD

@@ -0,0 +1,32 @@
+load("//tools:defs.bzl", "go_library")
+load("//tools/go_generics:defs.bzl", "go_template_instance")
+
+package(licenses = ["notice"])
+
+go_template_instance(
+    name = "message_list",
+    out = "message_list.go",
+    package = "msgqueue",
+    prefix = "msg",
+    template = "//pkg/ilist:generic_list",
+    types = {
+        "Element": "*Message",
+        "Linker": "*Message",
+    },
+)
+
+go_library(
+    name = "msgqueue",
+    srcs = [
+        "msgqueue.go",
+        "message_list.go",
+    ],
+    visibility = ["//pkg/sentry:internal"],
+    deps = [
+        "//pkg/sentry/kernel/auth",
+        "//pkg/sentry/kernel/ipc",
+        "//pkg/sentry/kernel/time",
+        "//pkg/waiter",
+        "//pkg/sync",
+    ],
+)