use decls from Rinterface.h and Rembedded.h when available

Author: s-u

src/jri/src/Rdecl.h

@@ -2,11 +2,24 @@
 #define __RDECL_H__
 
 /* declarations from R internals or other include files */
-/* last update: R 2.4.0 */
+/* last update: R 4.6.0 */
 
+#include <Rversion.h>
+
+#define R_INTERFACE_PTRS 1
+#define CSTACK_DEFNS 1
+#include <Rinterface.h> /* R_ReadConsole since 4.6.0 */
+
+/* some have been added to R 4.6.0 */
+#if R_VERSION >= R_Version(4,6,0)
+#include <Rembedded.h>  /* run_Rmainloop (since 4.6.0), Rf_initialize_R (since 2.4.0) */
+#else
 void run_Rmainloop(void); /* main/main.c */
 int  R_ReadConsole(char*, unsigned char*, int, int); /* include/Defn.h */
+int  Rf_initialize_R(int ac, char **av); /* include/Rembedded.h - exists since 2.4.0 */
+#endif /* R < 4.6.0 */
+
+/* this one is still left over */
 void Rf_checkArity(SEXP, SEXP); /* include/Defn.h */
-int  Rf_initialize_R(int ac, char **av); /* include/Rembedded.h */
 
-#endif
+#endif /* __RDECL_H__ */

src/jri/src/Rinit.c

@@ -2,17 +2,14 @@
 #include <Rinternals.h>
 #include "Rinit.h"
 #include "Rcallbacks.h"
-#include "Rdecl.h"
+#include "Rdecl.h" /* includes Rinterface.h */
 
 /*-------------------------------------------------------------------*
  * UNIX initialization (includes Darwin/Mac OS X)                    *
  *-------------------------------------------------------------------*/
 
 #ifndef Win32
 
-#define R_INTERFACE_PTRS 1
-#define CSTACK_DEFNS 1
-#include <Rinterface.h>
 /* and SaveAction is not officially exported */
 extern SA_TYPE SaveAction;