[Ada] Further cleanup in inlining machinery

This is visible if you pass a very small number by means of -gnateinn.

2019-08-14  Eric Botcazou  <ebotcazou@adacore.com>

gcc/ada/

	* inline.adb (Add_Pending_Instantiation): Fix off-by-one error
	in the comparison against the maximum number of instantiations.

From-SVN: r274472

gcc/ada/ChangeLog

 2019-08-14  Eric Botcazou  <ebotcazou@adacore.com>
 
+	* inline.adb (Add_Pending_Instantiation): Fix off-by-one error
+	in the comparison against the maximum number of instantiations.
+
+2019-08-14  Eric Botcazou  <ebotcazou@adacore.com>
+
 	* inline.adb (Add_Pending_Instantiation): Use greater-or-equal
 	in the comparison against the maximum number of instantiations.
 

gcc/ada/inline.adb

@@ -794,7 +794,7 @@ package body Inline is
       --  Here is a defense against a ludicrous number of instantiations
       --  caused by a circular set of instantiation attempts.
 
-      if Pending_Instantiations.Last >= Maximum_Instantiations then
+      if Pending_Instantiations.Last + 1 >= Maximum_Instantiations then
          Error_Msg_Uint_1 := UI_From_Int (Maximum_Instantiations);
          Error_Msg_N ("too many instantiations, exceeds max of^", Inst);
          Error_Msg_N ("\limit can be changed using -gnateinn switch", Inst);