Mike Fleetwood authored Aug 31, 2023 and Curtis Gedak committed Sep 23, 2023

In C++11, nullptr [1] is the strongly typed value to use instead of the
macro NULL [2].  Use everywhere [3][4].

[1] nullptr, the pointer literal (since C++11)
    https://en.cppreference.com/w/cpp/language/nullptr
[2] NULL
    https://en.cppreference.com/w/cpp/types/NULL
[3] Bjarne Stroustrup's C++ Style and Technique FAQ, Should I use NULL
    or 0?
    https://www.stroustrup.com/bs_faq2.html#null
        "In C++, the definition of NULL is 0, so there is only an
        aesthetic difference.  I prefer to avoid macros, so I use 0.
        Another problem with NULL is that people sometimes mistakenly
        believe that it is different from 0 and/or not an integer.  In
        pre-standard code, NULL was/is sometimes defined to something
        unsuitable and therefore had/has to be avoided.  That's less
        common these days.

        If you have to name the null pointer, call it nullptr; that's
        what it's called in C++11.  Then, "nullptr" will be a keyword.
        "
[4] What is nullptr in C++? Advantages, Use Cases & Examples
    https://favtutor.com/blogs/nullptr-cpp
        "Advantages of nullptr
        ...
        Compatible: Null pointers are compatible with null pointer
        constants in the C style (such as NULL and 0).  This implies
        that old C code that uses these constants and null pointers can
        communicate with each other in C++.
        "

Closes !117 - Require C++11 compilation