uclibc: enable libintl stubs

In order to avoid having to bring libintl from gettext whenever you
want to build a program that needs it, uClibc-ng now provides a stub
implementation of the gettext functions in uClibc-ng itself. This
brings uClibc-ng in the same situation as musl.

This will fix a lot of build failures related to static linking with
libintl, and generally is a first step to simplify our gettext
handling.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Reviewed-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>