Stop using LinearFifo in BufferedWriter
Stop using LinearFifo in BufferedWriter

Looking at the BufferedWriter assembly generated, one can see that is
has to do a lot of work, just to copy over some bytes and increase an
offset. This is because the LinearFifo is a much more general construct
than what BufferedWriter needs and the optimizer cannot prove that we
don't need to do this extra work.

andrewrk/zig,andrewrk/zig