anchor.diff:  | Visual Studio 2012 | 17.00.x.x    | 32/64-bit               |
   | Visual Studio 2013 | 18.00.x.x    | 32/64-bit               |
   | Visual Studio 2015 | 19.00.x.x    | 32/64-bit               |
  +| Visual Studio 2017 | 19.10.x.x    | 32/64-bit               |
   |=====
   
   [[vs1]]
  
positive.code: FlexDLL and OCaml are given <<seflexdll,later in this document>>.  Unless you
  bootstrap FlexDLL, you will need to ensure that the directory to which you
  install FlexDLL is included in your `PATH` environment variable. Note: if you
  use Visual Studio 2015, the binary distribution of FlexDLL will not work and
  you must build it from sources.
  
  The base bytecode system (ocamlc, ocaml, ocamllex, ocamlyacc, ...) of all three
  ports runs without any additional tools.
  
negative.code: 
  for 64-bit. For Visual Studio 2005-2013, you need to use one of the shortcuts in
  the "Visual Studio Tools" program group under the main program group for the
  version of Visual Studio you installed. For Visual Studio 2015 and 2017, you
  need to use the shortcuts in the "Windows Desktop Command Prompts" (2015) or
  "VC" (2017) group under the "Visual Studio Tools" group.
  
  Unlike `SetEnv` for the Windows SDK, the architecture is selected by using a
  different shortcut, rather than by running a command.
  