Split lines with many copyright years

Split lines with many copyright years

The new split_copyright_years.sh script can be run every few years to
keep the line length short enough for readability, and to avoid
clang-format wanting to change the lines such that the copyright
checker no longer recognizes a valid copyright statement.

Numerous files have now been bumped for 2020 because the copyright
line has been changed. That's technically valid.

In recent merge commits, several files were changed to use year ranges
like 2012-2020. Those have been reverted to the old style, which is
thought to be more valid.

Fixes #3282

Change-Id: I9c4e4677bf22a8d48ab1b3245de257c4bbaccf9f