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.cpp b/libmemunreachable/LeakFolding.cpp
index 2dff672..69f320c 100644
--- a/libmemunreachable/LeakFolding.cpp
+++ b/libmemunreachable/LeakFolding.cpp
@@ -22,6 +22,8 @@
 #include "Tarjan.h"
 #include "log.h"
 
+namespace android {
+
 // Converts possibly cyclic graph of leaks to a DAG by combining
 // strongly-connected components into a object, stored in the scc pointer
 // of each node in the component.
@@ -132,3 +134,5 @@
 
   return true;
 }
+
+}  // namespace android