bench: rub it in — monsters, stdin wins, busybox retired

Suites split into benchmarks/files/{lines,words} and
benchmarks/stdin/piping, with the monsters bolted onto the lines suite:
100M lines raced against coreutils (~2x win), 1B lines solo (~6-8s,
11 GB in one pass). Stdin redirects from regular files are now mmap'd
in count_stream, so the stdin suite wins too — up to 12.00x on words.

The ratio column now reports how many times faster fastwc is, not how
much of GNU's time it used. busybox was removed from the suite: it
stopped being a challenge and started being a participation trophy.
GNU wc's lone win — 1M lines by one millisecond on hand-tuned AVX-512
assembly — is now a historical footnote, and the README says so.

.gitignore

@@ -55,7 +55,11 @@ dkms.conf
 # ---> fastwc benchmarks
 benchmarks/tools/genfile
 benchmarks/.data/
+benchmarks/files/*/.data/
+benchmarks/stdin/piping/.data/
 benchmarks/FAILED-benchmark.txt
+benchmarks/files/*/FAILED-benchmark.txt
+benchmarks/stdin/piping/FAILED-benchmark.txt
 
 # ---> fastwc build artifacts
 bin/