compiling master fails

On Post 2.3 cyle (batch #5) (v2.3.1-167-g7f4ba4b)

    CC http.o
http.c: In function 'get_preferred_languages':
http.c:1021:2: warning: implicit declaration of function 'setlocale'
[-Wimplicit-function-declaration]
  retval = setlocale(LC_MESSAGES, NULL);
  ^
http.c:1021:21: error: 'LC_MESSAGES' undeclared (first use in this function)
  retval = setlocale(LC_MESSAGES, NULL);
                     ^
http.c:1021:21: note: each undeclared identifier is reported only once
for each function it appears in
make: *** [http.o] Error 1