Also introduces a new "inrange" function, useful for future refactorings
to std::vector

The mattrig macro expands the mw argument at one point into:

if (curmat != MAT_WATER ? S_SPLASH2 : S_SPLASH1 >= 0)

Co-authored-by: Robert Alm Nilsson <[email protected]>

There should be no reason to overwrite this as the C++ spec already
specifies it. Compilers nowadays also gift us a dedicated warning for this
kind of situation (-Wzero-as-null-pointer-constant).

Remove it and specify <cstddef> to still make NULL accessible.

This usage of volatile has been deprecated since C++20: use std::atomic
in its place.

Deprecated in C++20

Enable new language features that allow everyone to write better, safer and
faster C++ code (and not let the game die).

As of C++17, we can specify whether we want our switch cases to
fall-through or not (in presence of a break statement): specifying these
avoids unnecessary compiler warnings and makes the code clearer as to what
it is doing.

Specify the fallthrough attribute where needed and replace the comments
that specify its explicit usage.

As of C++17, the STL already provides us with std::clamp which in turn
makes the implementation here provided redundant and possibly broken:
remove the implementation here defined and use the one provided by
<algorithm>.

As of C++20, the STL already provides us with mathematical constants that
make the macro-fied ones used in tools redundant and possibly inaccurate:
remove our definitions of the macros and use the constants defined in the
<numbers> header.