Update some deprecated Starlark function calls

The `ctx.action()` call and friends are now under `ctx.actions.*`.
This patch updates the calls to the new locations. Newer bazel
versions removed the old versions altogether.

Change-Id: I748d056054d13a0385a06c0c94a2283acfdb82af
diff --git a/third_party/protobuf/protobuf.bzl b/third_party/protobuf/protobuf.bzl
index 9589750..7925d18 100644
--- a/third_party/protobuf/protobuf.bzl
+++ b/third_party/protobuf/protobuf.bzl
@@ -105,7 +105,7 @@
     inputs += [plugin]
 
   if args:
-    ctx.action(
+    ctx.actions.run(
         inputs=inputs,
         outputs=ctx.outputs.outs,
         arguments=args + import_flags + [s.path for s in srcs],
@@ -130,7 +130,7 @@
         "protoc": attr.label(
             cfg = "host",
             executable = True,
-            single_file = True,
+            allow_single_file = True,
             mandatory = True,
         ),
         "plugin": attr.label(