[v3] Mini-tweak to acinclude.m4

[Paolo Carlini]

Hi,

I don't think we have any reason to trigger a -Wwrite-strings warning, 
thus, barring objections, I'm going to commit the below.

Thanks,
Paolo.

///////////////////////
2014-05-08  Paolo Carlini  <paolo.carl...@oracle.com>

        * acinclude.m4 ([GLIBCXX_ENABLE_C99]): Avoid -Wwrite-strings warning.
        * configure: Regenerate.
Index: acinclude.m4
===================================================================
--- acinclude.m4        (revision 210183)
+++ acinclude.m4        (working copy)
@@ -1052,8 +1052,8 @@ AC_DEFUN([GLIBCXX_ENABLE_C99], [
        vscanf("%i", args);
        vsnprintf(fmt, 0, "%i", args);
        vsscanf(fmt, "%i", args);
-      }],
-     [snprintf("12", 0, "%i");],
+       snprintf(fmt, 0, "%i");
+      }], [],
      [glibcxx_cv_c99_stdio=yes], [glibcxx_cv_c99_stdio=no])
   ])
   AC_MSG_RESULT($glibcxx_cv_c99_stdio)