C++17

With this change C++17 language features can be used in code that does
not need to be be included in client code (not in public headers or
the files they transitively include).

We haven't investigated the c++17ness of the standard libraries in use
by clients so proceed with caution on library features.

One thing discovered along the way: throw() in C++17 is now equivalent
to noexcept(true). Moreover, the noexcept-ness of a function is part of
its type in C++17. This means that if a header declares a function with
throw() and it is included in a cpp compiled with C++17 file it will have
a different type than if it is compiled in a file compiled with C++14 (or
earlier) and you can get linker errors. Here is a change we had to make
as a result of this:

https://skia.googlesource.com/skia.git/+/4d0fe38f29388ef0aa6893d1d4fc237e758dd11f%5E%21/#F0

Change-Id: I996f2237fdd6b49e2e4cc8d3ff6db9dd536eafd8
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/235022
Commit-Queue: Brian Salomon <bsalomon@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
2 files changed