Split hardware mapping from `fifo.ys` into `fifo_map.ys`. Reduces size of `fifo.out` log and allows separate yosys calls in the makefile.
Some tidy up and minor changes in `fifo.ys` for better discussion.
Filled out note on `clean` (changed from `opt_clean`) and introduced `;;`.
Highlighted `$memrd` and added a paragraph about it.
More detail on the flatten and merging of `fifo_reader` block.
Brief discussion on the changes from `$memrd` to `$memrd_v2`.
