[bug-gettext] English fallback bug on macOS.

[Nate Weaver]

Hello,

When LANG (etc.) aren't set, gettext doesn't break early when finding English 
in the list of preferred languages on macOS; this is because it only checks for 
the exact string "en" and not a prefix. This worked on older versions of macOS 
(e.g., 10.2) where the language code set *was* actually just "en", but it 
breaks on newer versions where the language code is "en-US" or "en-GB" or 
whatever. This can make things that don't include an english localization file 
(like Git) display messages in an incorrect language when the language 
preference order is English -> Other Localized Language (e.g., German or 
French).

What fixed it for me (and didn't seem to break other languages), is simply 
replacing both occurrences of

    if (strcmp (buf, "en") == 0)

with

    if (strncmp (buf, "en", 2) == 0)

Let me know if you want a patchfile or anything, though I'm sure you won't need 
one!

--Nate Weaver (Wevah)