c521b69ffb
Since C++17 there is also std::string_view, which is similar to StringRef. This commit does a couple of things: * New implicit conversions between StringRef and std::string_view. * Support std::string_view in blender::DefaultHash. * Support most of the methods that std::string_view has. * Add StringRef::not_found which can be used instead of -1 in some places. * Improve/fix the description at the top of BLI_string_ref.hh.