android-ndk r10b

Previously the formula produced wrong directory structure. I've fixed it to be the same as when performing the following commands:
```
tar xf android-ndk32-r10b-darwin-x86_64.tar.bz2
tar xf android-ndk64-r10b-darwin-x86_64.tar.bz2
```
Why is this installing a `ndk32` on 64-bit?