dev-python/typing-extensions: Add typing-extensions 3.7.4.1 from upstream

Copied from https://github.com/gentoo/gentoo.git at commit
82f12930ff6f90b237815b66a2dc93960bac9182 with KEYWORDS replaced with
"*".

BUG=b:162009542
TEST=sudo emerge mypy

Change-Id: I8ac3a89951b6509078c78e2ee569aa376d19fc88
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/overlays/portage-stable/+/2316393
Tested-by: Tom Hughes <tomhughes@chromium.org>
Auto-Submit: Tom Hughes <tomhughes@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Commit-Queue: Tom Hughes <tomhughes@chromium.org>
3 files changed