Part 1 of #301908.
This renames the two versions of the Apple Public Source License seen in
nixpkgs; `apsl20` was often confused as being for the widely-used Apache
License 2.0.
If things build fine with `stdenvNoCC`, let them use that. If tools
might be prefixed, prepare for that, either by directly splicing or just
using the env vars provided by the wrapper setup-hooks.
Co-authored-by: Dmitry Kalinkin <dmitry.kalinkin@gmail.com>
This also changes the versioning scheme to be in more "human-meaningful"
terms, so instead of the internal release numbers we talk about 10.10.5
or 10.9.5.