intl.m4: check for NL_LOCALE_NAME fails with CFLAGS=-Wall -Werror

[Marti Raudsepp]

Hello,

In the intl.m4 autoconf macro, the check for NL_LOCALE_NAME macro
fails when CFLAGS include both -Wall and -Werror, because GCC is
warning about an unused variable.

I'm using gettext version 0.16.1.

Here's the relevant snippet from config.log:
  configure:24553: gcc -o conftest -O0 -g3 -Werror -Wall
-I/usr/include/neon   conftest.c -lreadline  -lcurses >&5
  cc1: warnings being treated as errors
  conftest.c: In function 'main':
  conftest.c:131: warning: unused variable 'cs'
  configure:24559: $? = 1
  configure: failed program was:
  | /* confdefs.h.  */
  [...]
  | #define _GNU_SOURCE 1
  [...]
  | /* end confdefs.h.  */
  | #include <langinfo.h>
  | #include <locale.h>
  | int
  | main ()
  | {
  | char* cs = nl_langinfo(_NL_LOCALE_NAME(LC_MESSAGES));
  |   ;
  |   return 0;
  | }
  configure:24577: result: no

This should be straightforward to fix.

Regards,
Marti Raudsepp