* See #204 - zig build system
* allow builtin types Os, Environ, Arch to be used at runtime.
they have zero_bits=false and debug info now.
* Eradicate use of `@alloca` in std for syscalls. See #225
* add `std.io.writeFile`
* `std.debug.panic` adds a newline to format
* In-progress os.ChildProcess.spawn implementation. See #204
* Add explicit cast from integer to error. Closes#294
* fix casting from error to integer
* fix compiler crash when initializing variable to undefined
with no type
