Extend tidy license check to remaining source code

[brson]

make tidy checks the license of files but tidy is only run on a subset of the repository since some third party, tests and overlooked code isn't checked for formatting. We need to extend the tidy check to all source code, even tests (I think).

[catamorphism]

Another thing to add to the tidy license checking: checking the copyright year that appears at the top of the file. Graydon said this should be a list or range of years in which significant changes were made. So many files will have to change from 2012 (as they are now) to 2011-2013 or some other such thing.

[graydon]

I think this is done now, no?

[catamorphism]

@graydon It seems like it's not -- tidy isn't being run on tests (so that tests aren't required to have the 100-column limit), but tidy calls the license script. So the tests aren't being checked for licenses at all. Unless I'm missing something.

[catamorphism]

Nominating for milestone 5, production-ready -- we probably have to bite the bullet and do this sooner than later.

[catamorphism]

Accepted for milestone 5

[dguenther]

Once #12055 lands, are there any other areas that need checking? Right now it appears we run tidy on:

• *.r[sc] except in libuv, llvm, and gyp
• *.cpp in rt, rt/*, rt/*/*, and rustllvm except miniz.cpp and in rt/sundown
• *.h in rt, rt/*, rt/*/*, and rustllvm except rt/vg/valgrind.h, rt/vg/memcheck.h, rt/msvc/typeof.h, rt/msvc/stdint.h, rt/msvc/inttypes.h, and in rt/sundown
• *.py in etc

[pnkfelix]

P-low. This issue is almost done, according to @brson.

[brson]

@dguenther The only remaining missing licenses I'm aware of are in src/doc. There are some scripts there that should have the license block, but more importantly the docs themselves do not have a license declared but should (#12069). I'd consider the doc licenses to be a separate issue, so once the scripts are all covered this issue is done.