xine was already checking for MIN/MAX macros but the replacement does not
work (at least not on mingw32). This change defines HAVE_[MIN|MAX]_MACRO and
if missing, providedes them in lib/os_internal.h

The MIN/MAX macro are quite often used on the source code to find the
minimum or maximum value between two, instead of defining it per-unit,
check if the system provides them include the right header, otherwise
define them during configure run.

timegm.c uses tzset(), but if host does not provide it, compilation or
linking will fail. I fixed it by checking the status of HAVE_TZSET. If the
function is not detected at configure time, it won't be used, like it has
been done in other parts of xine-lib.

As the source file for xine_private_strndup() does not provide a licence
header, replace it with a safe copy (licence wise) taken from NetBSD CVS.

The implementation is licensed under 3-clause BSD licence, that is
compatible with GPL-2 or later.

As the source file for xine_private_strsep() does not provide a licence
header, replace it with a safe copy (licence wise) taken from OpenBSD CVS.

The implementation is licensed under 3-clause BSD licence, that is compatible
with GPL-2 or later.

--HG--
extra : transplant_source : %E0%D0%C5%8B%BEU%DD%24%5D7%1F%ADV%AD%EB%23%CBU%80%EB

For contributed code, leave whatever the version we last synced for is using
to make simpler future syncs.