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/LeakFolding.h b/libmemunreachable/LeakFolding.h
index 740b54f..09affac 100644
--- a/libmemunreachable/LeakFolding.h
+++ b/libmemunreachable/LeakFolding.h
@@ -19,6 +19,8 @@
 
 #include "HeapWalker.h"
 
+namespace android {
+
 class LeakFolding {
  public:
   LeakFolding(Allocator<void> allocator, HeapWalker& heap_walker)
@@ -93,4 +95,6 @@
   allocator::vector<Allocator<SCCInfo>::unique_ptr> leak_scc_;
 };
 
+}  // namespace android
+
 #endif  // LIBMEMUNREACHABLE_LEAK_FOLDING_H_