PR modula2/110779 SysClock can not read the clock

This patch completes the implementation of the ISO module
SysClock.mod.  Three new testcases are provided.  wrapclock.{cc,def}
are new support files providing access to clock_settime, clock_gettime
and glibc timezone variables.

gcc/m2/ChangeLog:

	PR modula2/110779
	* gm2-libs-iso/SysClock.mod: Re-implement using wrapclock.
	* gm2-libs-iso/wrapclock.def: New file.

libgm2/ChangeLog:

	PR modula2/110779
	* config.h.in: Regenerate.
	* configure: Regenerate.
	* configure.ac (GM2_CHECK_LIB): Check for clock_gettime
	and clock_settime.
	* libm2iso/Makefile.am (M2DEFS): Add wrapclock.def.
	* libm2iso/Makefile.in: Regenerate.
	* libm2iso/wraptime.cc: Replace HAVE_TIMEVAL with
	HAVE_STRUCT_TIMEVAL.
	* libm2iso/wrapclock.cc: New file.

gcc/testsuite/ChangeLog:

	PR modula2/110779
	* gm2/iso/run/pass/m2date.mod: New test.
	* gm2/iso/run/pass/testclock.mod: New test.
	* gm2/iso/run/pass/testclock2.mod: New test.

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