Set tcl_library to the value of system variable

tcltklib.c.diff

diff --git a/ext/tk/tcltklib.c b/ext/tk/tcltklib.c
index 8701cfe..b058443 100644
--- a/ext/tk/tcltklib.c
+++ b/ext/tk/tcltklib.c
@@ -5614,6 +5614,7 @@ ip_init(argc, argv, self)

     /* from Tcl_AppInit() */
     DUMP1("Tcl_Init");
+    Tcl_SetVar(ptr->ip, "tcl_library", getenv("TCL_LIBRARY"), TCL_GLOBAL_ONLY);
     if (Tcl_Init(ptr->ip) == TCL_ERROR) {
         rb_raise(rb_eRuntimeError, "%s", Tcl_GetStringResult(ptr->ip));
     }