build-sys: missing header when NLS is disabled

build-sys: missing header when NLS is disabled

Compiling utils fail when disable NLS with the --disable-nls switch.
"mkfs.c:46: error: 'LC_ALL' undeclared (first use in this function)"
It is due to a missing locale.h header : When enabling NLS, nls.h
includes libintl.h, which in turn includes locale.h. When disabling NLS,
libintl.h isn't anymore included nor locale.h, which is needed for the
setlocale() calls.

Signed-off-by: Gabriel Barazer <gabriel@oxeva.fr>
Signed-off-by: Karel Zak <kzak@redhat.com>