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/ThreadCapture.cpp b/libmemunreachable/ThreadCapture.cpp
index a7bd91c..45eb55d 100644
--- a/libmemunreachable/ThreadCapture.cpp
+++ b/libmemunreachable/ThreadCapture.cpp
@@ -39,6 +39,8 @@
 #include "Allocator.h"
 #include "log.h"
 
+namespace android {
+
 // bionic interfaces used:
 // atoi
 // strlcat
@@ -361,3 +363,5 @@
 void ThreadCapture::InjectTestFunc(std::function<void(pid_t)>&& f) {
   impl_->InjectTestFunc(std::forward<std::function<void(pid_t)>>(f));
 }
+
+}  // namespace android