Motivated by `std::string_view` being usable in
const (compile-time) context.
One functional change was needed for StringRef:
`std::char_traits<char>::length(str)` instead of `strlen`.
Reviewed By: JacquesLucke, LazyDodo
Differential Revision: https://developer.blender.org/D9788
The new reverse iterators behave as the reverse iterators for contains from
the standard library. Have a look at the tests to see how to use them.
Using them will hopefully become easier with ranges in C++20.
A Vector can now be constructed from two iterators, which is very common
in the standard library.
New Vector.insert methods allow adding elements in the middle of a vector.
These methods should not be used often in practice, because they has a linear running time.
New Vector.prepend methods allow adding elements to the beginning of a vector.
These methods are O(n) as well.
