implement uselocale function (minimal)

[musl] / src / locale / uselocale.c

#include "locale_impl.h"
#include "pthread_impl.h"

locale_t uselocale(locale_t l)
{
        pthread_t self = pthread_self();
        locale_t old = self->locale;
        if (l) self->locale = l;
        return old;
}