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/builtins.h b/init/builtins.h
index e1f0567..b110f61 100644
--- a/init/builtins.h
+++ b/init/builtins.h
@@ -24,6 +24,9 @@
 
 #include "keyword_map.h"
 
+namespace android {
+namespace init {
+
 using BuiltinFunction = std::function<int(const std::vector<std::string>&)>;
 class BuiltinFunctionMap : public KeywordMap<BuiltinFunction> {
   public:
@@ -33,4 +36,7 @@
     const Map& map() const override;
 };
 
+}  // namespace init
+}  // namespace android
+
 #endif