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/ProcessMappings.cpp b/libmemunreachable/ProcessMappings.cpp
index 42e5326..9a06870 100644
--- a/libmemunreachable/ProcessMappings.cpp
+++ b/libmemunreachable/ProcessMappings.cpp
@@ -25,6 +25,8 @@
 #include "ProcessMappings.h"
 #include "log.h"
 
+namespace android {
+
 // This function is not re-entrant since it uses a static buffer for
 // the line data.
 bool ProcessMappings(pid_t pid, allocator::vector<Mapping>& mappings) {
@@ -64,3 +66,5 @@
   }
   return true;
 }
+
+}  // namespace android