Log message:
Mass-change BUILD_DEPENDS to TOOL_DEPENDS outside mk/.

Almost all uses, if not all of them, are wrong, according to the
semantics of BUILD_DEPENDS (packages built for target available for
use _by_ tools at build-time) and TOOL_DEPEPNDS (packages built for
host available for use _as_ tools at build-time).

No change to BUILD_DEPENDS as used correctly inside buildlink3.

As proposed on tech-pkg:
https://mail-index.netbsd.org/tech-pkg/2023/06/03/msg027632.html

Log message:
lang/hamlet: import hamlet-2.0.0

HaMLet is a faithful and complete implementation of the Standard
ML programming language (SML'97). It aims to be

  * an accurate reference implementation of the language specification,
  * a platform for experimentation with the language semantics or
    extensions to it,
  * a useful tool for educational purposes.

The implementation is intended to be as direct a translation of
the language formalisation found in the Definition of Standard ML
as possible, modulo bug fixes. It tries hard to get all details of
the Definition right. The HaMLet source code

  * implements complete Standard ML,
  * closely follows the structure of the Definition, with lots of
    cross references,
  * conforms to the latest version of the Standard ML Basis Library,
    is written entirely in Standard ML, with the ability to bootstrap,
  * may readily be compiled with SML/NJ, MLton, Moscow ML, Poly/ML,
    Alice ML, the ML Kit, or SML#.