* `std.Buffer.print` is removed; use `buffer.outStream().print`
* `std.fmt.count` returns a `u64`
* `std.Fifo.print` is removed; use `fifo.outStream().print`
* `std.fmt.bufPrint` error is renamed from `BufferTooSmall`
to `NoSpaceLeft` to match `std.os.write`.
* `std.io.FixedBufferStream.getWritten` returns mutable buffer
if the buffer is mutable.
Thanks to the Windows Process Environment Block, it is possible to
obtain handles to the standard input, output, and error streams without
possibility of failure.
* use erase rest of line escape code.
* use `stderr.supportsAnsiEscapeCodes` rather than `isTty`.
* respect `--color off`
* avoid unnecessary recursion
* add `Progress.log`
* disable the progress std lib test since it's noisy and uses
`time.sleep()`.
* enable/integrate progress printing with the default test runner
