Support functions for Android's class libraries

 libnativehelper is a collection of JNI related utilities used in
 Android.
 .
 There are several header and binary libraries here and not all of the
 functionality fits together well. The header libraries are mostly C++
 based. The binary libraries are entirely written in C with no C++
 dependencies. This is by design as the code here can be distributed in
 multiple ways, including mainline modules, so keeping the size down
 benefits everyone with smaller downloads and a stable ABI.