rl_json package allow Tcl 9 and also a vs project for Windows

[escolano]

please, consider to add all or some of our commits to your repository,
in order to allow rl_json package for Tcl 9 (and also 8) for all platforms, and facilitate a vs (Visual studio) project to be compiled on Windows

[escolano]

to have compatility 8 - 9 is necessary to have this small tcl_compatibility_8_9.h somewhere (e.g. inside the tcltk folder)
tcl_compatibility_8_9.zip
that has this content:

// Check, if Tcl version supports Tcl_Size, which was introduced in Tcl 8.7 and 9.
#ifndef TCL_SIZE_MAX
#include <limits.h>
#define TCL_SIZE_MAX INT_MAX
#ifndef Tcl_Size
typedef int Tcl_Size;
#endif //Tcl_Size
#define TCL_SIZE_MODIFIER ""
#define Tcl_GetSizeIntFromObj Tcl_GetIntFromObj
#define Tcl_NewSizeIntObj Tcl_NewIntObj
typedef unsigned int TCL_HASH_TYPE;
#define TK_ANCHOR_NULL -1
#define TK_JUSTIFY_NULL -1
#endif //TCL_SIZE_MAX