strerrorname_np on GNU/Hurd

[Collin Funk]

Hi Bruno,

I noticed that test-strerrorname_np.c fails on the following line on
GNU/Hurd:

    /* GNU/Hurd */
    #if defined ED_ALREADY_OPEN
    ASSERT (strcmp (strerrorname_np (ED_ALREADY_OPEN), "ED_ALREADY_OPEN") == 0);
    #endif

This is because glibc doesn't have GNU/Hurd errors in
sysdeps/gnu/errlist.h. This includes EMACH_*, EKERN_*, EMIG_*, and ED_*.

How about I #if 0 these checks out in the tests and Gnulib replacement
function for now so the behaviors are the same? I can write a bug report
and we can see if they get added.

Collin