init: create android::init:: namespace

With some small fixups along the way

Test: Boot bullhead
Test: init unit tests
Change-Id: I7beaa473cfa9397f845f810557d1631b4a462d6a
diff --git a/init/service.h b/init/service.h
index b9c270a..3c7dc74 100644
--- a/init/service.h
+++ b/init/service.h
@@ -55,8 +55,8 @@
 
 #define NR_SVC_SUPP_GIDS 12    // twelve supplementary groups
 
-class Action;
-class ServiceManager;
+namespace android {
+namespace init {
 
 struct ServiceEnvironmentInfo {
     ServiceEnvironmentInfo();
@@ -236,4 +236,7 @@
     std::unique_ptr<Service> service_;
 };
 
+}  // namespace init
+}  // namespace android
+
 #endif