This patch defensively checks for every C function and every struct
used in wrapclock.cc.  It adds return values to GetTimespec and
SetTimespec to allow the module to return a code representing
unavailable.

gcc/m2/ChangeLog:

	PR modula2/110779
	* gm2-libs-iso/SysClock.mod (GetClock): Test GetTimespec
	return value.
	(SetClock): Test SetTimespec return value.
	* gm2-libs-iso/wrapclock.def (GetTimespec): Add integer
	return type.
	(SetTimespec): Add integer return type.

libgm2/ChangeLog:

	PR modula2/110779
	* config.h.in: Regenerate.
	* configure: Regenerate.
	* configure.ac (AC_CACHE_CHECK): Check for tm_gmtoff field in
	struct tm.
	(GM2_CHECK_LIB): Check for daylight, timezone and tzname.
	* libm2iso/wrapclock.cc (timezone): Guard against absence of
	struct tm and tm_gmtoff.
	(daylight): Check for daylight.
	(timezone): Check for timezone.
	(isdst): Check for isdst.
	(tzname): Check for tzname.
	(GetTimeRealtime): Check for struct timespec.
	(SetTimeRealtime): Check for struct timespec.
	(InitTimespec): Check for struct timespec.
	(KillTimespec): Check for struct timespec.
	(SetTimespec): Check for struct timespec.
	(GetTimespec): Check for struct timespec.

Signed-off-by: Gaius Mulley <gaiusmod2@gmail.com>