Move libmemunreachable into namespace android

Putting libmemunreachable in the global C++ namespace was an oversight,
move it into namespace android.

Test: m -j checkbuild
Change-Id: I0799906f6463178cb04a719bb4054cad33a50dbe
diff --git a/libmemunreachable/ScopedAlarm.h b/libmemunreachable/ScopedAlarm.h
index 53ea112..bb50b9e 100644
--- a/libmemunreachable/ScopedAlarm.h
+++ b/libmemunreachable/ScopedAlarm.h
@@ -23,6 +23,8 @@
 #include <chrono>
 #include <functional>
 
+namespace android {
+
 class ScopedAlarm {
  public:
   ScopedAlarm(std::chrono::microseconds us, std::function<void()> func) {
@@ -49,4 +51,7 @@
  private:
   static std::function<void()> func_;
 };
+
+}  // namespace android
+
 #endif