Bitmap C++ wrapper API

Forked from https://github.com/android-ndk/ndk/issues/476

Possible API:

```C++
namespace android::graphics {
class Bitmap final {
public:
Bitmap (JNIEnv *env, jobject jbitmap);
~Bitmap (); // Use RAII to release the bitmap/unlock it

int getInfo (AndroidBitmapInfo& info);
int lockPixels (void **addrPtr);
int unlockPixels ();

// other nice to have, 2D drawing member functions
};
}
```

The issue names no repository files, tests, or entry points. Read the linked Android NDK issue 476 and evaluate the proposed Bitmap API, including RAII and the optional drawing functions. Done requires an agreed scope and an implemented, reviewed C++ wrapper API.

Written by the indexing model from the issue text.