lib/tt: fix langinfo build break

lib/tt: fix langinfo build break

When HAVE_LANGINFO_H is not defined we break the compilation in tt.c:

  CC     tt.o
tt.c: In function ‘tt_new_table’:
tt.c:142: warning: implicit declaration of function ‘nl_langinfo’
tt.c:142: error: ‘CODESET’ undeclared (first use in this function)
tt.c:142: error: (Each undeclared identifier is reported only once
tt.c:142: error: for each function it appears in.)
make: *** [tt.o] Error 1

Signed-off-by: Davidlohr Bueso <dave@gnu.org>