cpitf.c, MS Visual Studio, introduce csh variable "pg_config"

reflecting .exe compilation for
  32/64 bit
  with/without NGDEBUG

src/frontend/cpitf.c

@@ -223,6 +223,23 @@ ft_cpinit(void)
     /* Reset this for the front end. */
     cp_hash = '*';
 
+    /* set variables to read program configuration into special spinit for VS */
+#ifdef _MSC_VER
+#ifdef CONFIG64
+#ifdef NGDEBUG
+    cp_vset("pg_config", CP_STRING, "d64");
+#else
+    cp_vset("pg_config", CP_STRING, "r64");
+#endif
+#else
+#ifdef NGDEBUG
+    cp_vset("pg_config", CP_STRING, "d32");
+#else
+    cp_vset("pg_config", CP_STRING, "r32");
+#endif
+#endif
+#endif
+
     /* NGSPICEDATADIR has been set to path "$dprefix/share/ngspice" in configure.ac,
        Spice_Lib_Dir has been set to NGSPICEDATADIR in conf.c,
        may be overridden by environmental variable SPICE_LIB_DIR in ivars().