[wip] Android 3

'yet another' attempt at getting android building. have fought many demons here, but the big one remaining is libpng, that just refuses to budge. now trying to cross-compile libpng, and it compiles but apparently `ar` or some other utility is generating a `.a` file that is unreadable by android's build tools, despite passing what I think are the right options to `./configure`

current failure state: https://gist.githubusercontent.com/tmcw/874561dc555ca2a71a04/raw/d80c1da344b2989282e00bf2eebf69ace81d8887/msg.txt

To setup:

* `git clone`
* `cp -r src jni/`
* `./android-bootstrap.sh`
* `libpng.sh`
* `ndk-build`

Stuff that needed hacking:

* pthreads is incomplete on android
* so is std::to_string and std::round
* android really wants you to have src in `jni`
* a bunch of files required explicit includes like `<stdlib.h>` where they compile fine on other platforms

Non-functional stubs:

* [ ] Request: this will require either a cross-compile of curl or jni bindings. Out of those two gnarly options, I lean towards libcurl, if cross-compiling ever starts to like me
* [ ] Settings doesn't do anything yet
* [ ] Still needs a JNI interface binding so anything can be called from Java-land

would love some wisdom re: how to dig out of this hole, running out of random keys i push here /cc @kkaefer @springmeyer