[Ada] Ensure constructor is a C++ constructor

2019-10-10  Arnaud Charlet  <charlet@adacore.com>

gcc/ada/

	* freeze.adb (Freeze_Subprogram): Ensure constructor is a C++
	constructor.

From-SVN: r276835

gcc/ada/ChangeLog

-2019-10-10  Gary Dismukes  <dismukes@adacore.com>
+2019-10-10  Arnaud Charlet  <charlet@adacore.com>
 
-	* libgnat/a-ststio.ads (File_Type): Apply pragma
-	Preelaborable_Initialization to the type.
\ No newline at end of file
+	* freeze.adb (Freeze_Subprogram): Ensure constructor is a C++
+	constructor.
\ No newline at end of file

gcc/ada/freeze.adb

@@ -8780,6 +8780,7 @@ package body Freeze is
       --  (either in pragma CPP_Constructor or in a pragma import).
 
       if Is_Constructor (E)
+        and then Convention (E) = Convention_CPP
         and then
            (No (Interface_Name (E))
               or else String_Equal