* introduce std.atomic.Int
* add src-self-hosted/test.zig which is tested by the main test suite
- it fully utilizes the multithreaded async/await event loop so the
tests should Go Fast
* `stage2/bin/zig build-obj test.zig` is able to spit out an error if 2 exported
functions collide
* ability for `zig test` to accept `--object` and `--assembly`
arguments
* std.build: TestStep supports addLibPath and addObjectFile
Andrew Kelley