cmake: Update android.toolchain.cmake from upstream.

From https://github.com/taka-no-me/android-cmake/commit/763b9f6ec43bf66f3b586669b68b9b6374c8f4b5

Fixes issue #293 for r9* NDKs.
doc: Rename DEVELOPMENT.markdown as HACKING.markdown.

"Hacking" seems more descriptive and more common.