modula-2: Fix registration of modules via constructors [PR108183].

modula-2: Fix registration of modules via constructors [PR108183].

This reworks the mechanism used for module registration to use init-
time constructors.  The order of registration is not important, the
actual initialization dependency tree will be computed early in the
execution (all that matters is that we have registered before that).

This fixes a potential issue in which the external name known to the
m2 system is of the form _M2_XXXXXX_ctor() but the C++ code was
producing a static variable instance with the same name.

Signed-off-by: Iain Sandoe <iain@sandoe.co.uk>
	PR modula2/108183

gcc/m2/ChangeLog:

	* gm2-libs-ch/UnixArgs.cc (_M2_UnixArgs_ctor): Rework to use
	an extern "C" function with 'constructor' attribute.
	* gm2-libs-ch/dtoa.cc (_M2_dtoa_ctor): Likewise.
	* gm2-libs-ch/ldtoa.cc (_M2_ldtoa_ctor): Likewise.

libgm2/ChangeLog:

	* libm2cor/KeyBoardLEDs.cc (_M2_KeyBoardLEDs_ctor): Rework to use
	an extern "C" function with 'constructor' attribute.
	* libm2iso/ErrnoCategory.cc (_M2_ErrnoCategory_ctor): Likewise.
	* libm2iso/RTco.cc (_M2_RTco_ctor): Likewise.
	* libm2pim/Selective.cc (_M2_Selective_ctor): Likewise.
	* libm2pim/SysExceptions.cc (_M2_SysExceptions_ctor): Likewise.
	* libm2pim/UnixArgs.cc (_M2_UnixArgs_ctor): Likewise.
	* libm2pim/cgetopt.cc (_M2_cgetopt_ctor): Likewise.
	* libm2pim/dtoa.cc (_M2_dtoa_ctor): Likewise.
	* libm2pim/errno.cc (_M2_errno_ctor): Likewise.
	* libm2pim/ldtoa.cc (_M2_ldtoa_ctor): Likewise.
	* libm2pim/sckt.cc (_M2_sckt_ctor): Likewise.
	* libm2pim/termios.cc (_M2_termios_ctor): Likewise.
	* libm2pim/wrapc.c: Add a new line to the file end.