This updates all source files to use a new standard header for copyright
and license declaration. Notably, copyright no longer includes a date,
and we now use the standard SPDX-License-Identifier header.
This commit was done almost entirely mechanically with perl, and then
some minimal manual fixes.
Updates #6865
Signed-off-by: Will Norris <will@tailscale.com>
This makes it easy to compact slices that contain duplicate elements
by sorting and then uniqing.
This is an alternative to constructing an intermediate map
and then extracting elements from it. It also provides
more control over equality than using a map key does.
Signed-off-by: Josh Bleecher Snyder <josh@tailscale.com>
