Project files were not following the clang-format style. For people
using IDEs were clang-format is always run after a save this would
cause unwanted changes.
This commit only applies "clang-format -i" to files.
* initializer_list overload returns by value to avoid lifetime issues
* generic overload uses expression SFINAE to work with any type that has member size() and operator[], which notably includes const/non-const vector and array.
* Add test coverage for const objects, rvalue initializer_lists, and constexpr usage.
Fixes#357.
* Nest "gsl" directory inside a new "include" directory.
* Cleanup the _MSC_VER conditionals a bit; use constexpr on VS2017+.
* Don't #define noexcept on non-Microsoft implementations.
* Workaround VS2017 bug in multi_span. (Also implement == and != for static_bounds_dynamic_range_t because I'm an EoP semantic soundness snob.)
Fixes#441.
