[Patch, obvious] Guard inform with warning return value

[Paolo Carlini]

Hi,

noticed this nit in a conditional for c++11 attributes. I'm going to 
commit the below as obvious.

Thanks,
Paolo.

/////////////////////
2015-07-03  Paolo Carlini  <paolo.carl...@oracle.com>

        * attribs.c (decl_attributes): Guard inform with the return value
        of the preceding warning.
Index: attribs.c
===================================================================
--- attribs.c   (revision 225384)
+++ attribs.c   (working copy)
@@ -469,10 +469,10 @@ decl_attributes (tree *node, tree attributes, int
          /* This is a c++11 attribute that appertains to a
             type-specifier, outside of the definition of, a class
             type.  Ignore it.  */
-         warning (OPT_Wattributes, "attribute ignored");
-         inform (input_location,
-                 "an attribute that appertains to a type-specifier "
-                 "is ignored");
+         if (warning (OPT_Wattributes, "attribute ignored"))
+           inform (input_location,
+                   "an attribute that appertains to a type-specifier "
+                   "is ignored");
          continue;
        }