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.h b/libmemunreachable/ProcessMappings.h
index 81b33dc..a0e97e9 100644
--- a/libmemunreachable/ProcessMappings.h
+++ b/libmemunreachable/ProcessMappings.h
@@ -19,6 +19,8 @@
 
 #include "Allocator.h"
 
+namespace android {
+
 struct Mapping {
   uintptr_t begin;
   uintptr_t end;
@@ -33,4 +35,6 @@
 // the line data.
 bool ProcessMappings(pid_t pid, allocator::vector<Mapping>& mappings);
 
+}  // namespace android
+
 #endif  // LIBMEMUNREACHABLE_PROCESS_MAPPING_H_