Add NDK r10, arm64-v8a, x86_64, mips64 support.

From the ABI documentation.
"As you would expect, generated libraries will go into $PROJECT/libs/x86-64/, and will be embedded into your .apk under /lib/x86-64/."
So the lib folder is x86-64, but the arch is of course x86_64.
I don't know why they chose to name the folder x86-64...