Make definitions of some native functions available as expected by packages...

Make definitions of some native functions available as expected by packages that expect USE_RINTERNALS to be set.

com.oracle.truffle.r.native/include/ed_Rinternals

 /USE_RINTERNALS section/
 i
 #ifdef FASTR
+// packages defining USE_INTERNALS expect certain defs (e.g. isNull) to be there
+#ifdef USE_RINTERNALS
+#define USE_RINTERNALS_DEFS
+#endif
 #undef USE_RINTERNALS
 #else
 .
@@ -73,5 +77,16 @@ SEXP R_PreserveObject(SEXP);
 +1
 a
 #endif
+.
+/#ifdef USE_RINTERNALS/
+d
+i
+#if defined (USE_RINTERNALS_DEFS) && (defined (USE_RINTERNALS) || defined (FASTR))
+.
+/macro version of R_CheckStack/
+i
+#endif
+#ifdef USE_RINTERNALS
+
 .
 w Rinternals.h