[gegl] gegl-parallel.h: extend __cplusplus check

[Øyvind "pippin" Kolås <ok src gnome org>]

commit 0f1baf2909fdd989d8a6c27a765386d840383261
Author: Øyvind Kolås <pippin gimp org>
Date:   Mon Mar 30 23:26:22 2020 +0200

    gegl-parallel.h: extend __cplusplus check
    
    Only check the _cplusplus version when it is defined.

 gegl/gegl-parallel.h | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/gegl/gegl-parallel.h b/gegl/gegl-parallel.h
index a8d201c73..cdd23ba0d 100644
--- a/gegl/gegl-parallel.h
+++ b/gegl/gegl-parallel.h
@@ -120,6 +120,7 @@ void   gegl_parallel_distribute_area  (const GeglRectangle             *area,
                                        gpointer                         user_data);
 
 
+#ifdef __cplusplus
 #if __cplusplus >= 201103
 
 extern "C++"
@@ -194,6 +195,7 @@ gegl_parallel_distribute_area (const GeglRectangle        *area,
 }
 
 #endif /* __cplusplus >= 201103 */
+#endif
 
 
 G_END_DECLS