libxpm: add explicit gettext-native dependency

libxpm: add explicit gettext-native dependency

In an issue similar to "atk: add explicit gettext-native dependency"
(964ea8bfc455f6017dc834104d96b8f5aa40a5bc) we need to add gettext-native
to DEPENDS explicitly as the gettext class reduces dependencies in
native builds.

Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>