c++: fix comments suggesting to use %require

[Akim Demaille]

commit 032a52be6ee002016a22453365ffb4f578a15e4d
Author: Akim Demaille <address@hidden>
Date:   Thu Oct 3 08:31:50 2019 +0200

    c++: fix comments suggesting to use %require
    
    * data/skeletons/location.cc, data/skeletons/stack.hh: Here.

diff --git a/data/skeletons/location.cc b/data/skeletons/location.cc
index b72cd3d3..8a330b92 100644
--- a/data/skeletons/location.cc
+++ b/data/skeletons/location.cc
@@ -326,7 +326,7 @@ m4_ifdef([b4_position_file], [[
 // used to define is now defined in "]b4_location_file[".
 //
 // To get rid of this file:
-// 1. add 'require "3.2"' (or newer) to your grammar file
+// 1. add '%require "3.2"' (or newer) to your grammar file
 // 2. remove references to this file from your build system
 // 3. if you used to include it, include "]b4_location_file[" instead.
 
diff --git a/data/skeletons/stack.hh b/data/skeletons/stack.hh
index ac0a34d1..cc1c63f4 100644
--- a/data/skeletons/stack.hh
+++ b/data/skeletons/stack.hh
@@ -145,7 +145,7 @@ m4_ifdef([b4_stack_file],
 // used to define is now defined with the parser itself.
 //
 // To get rid of this file:
-// 1. add 'require "3.2"' (or newer) to your grammar file
+// 1. add '%require "3.2"' (or newer) to your grammar file
 // 2. remove references to this file from your build system.
 ]b4_output_end[
 ]])