* initial oss-fuzz friendly build
parts taken from libfmt, which I wrote and have the copyright to
* fix build error
* add script for building a corpus zip
see https://google.github.io/oss-fuzz/getting-started/new-project-guide/#seed-corpus
* fix zip command
* drop setting the C++ standard
* disable the minify fuzzer, does not pass oss-fuzz check-build test
* fix integer overflow in subnormal_power10
detected by oss-fuzz
https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=18714
* invoke the build like oss fuzz does
* document what the scripts are for and how to use them
* add a page about fuzzing
Paul Dreik