modula2: -Wcase-enum detect singular/plural and use switch during build

This patch generates a singular or plural message relating to the
number of enums missing.  Use -Wcase-enum when building of the
modula-2 libraries and m2/stage2/cc1gm2.

gcc/m2/ChangeLog:

	* Make-lang.in (GM2_FLAGS): Add -Wcase-enum.
	(GM2_ISO_FLAGS): Add -Wcase-enum.
	* gm2-compiler/M2CaseList.mod (EnumerateErrors): Issue
	singular or plural start text prior to the enum list.
	Remove unused parameter tokenno.
	(EmitMissingRangeErrors): New procedure.
	(MissingCaseBounds): Call EmitMissingRangeErrors.
	(MissingCaseStatementBounds): Call EmitMissingRangeErrors.
	* gm2-libs-iso/TextIO.mod: Fix spacing.

libgm2/ChangeLog:

	* libm2cor/Makefile.am (libm2cor_la_M2FLAGS): Add
	-Wcase-enum.
	* libm2cor/Makefile.in: Regenerate.
	* libm2iso/Makefile.am (libm2iso_la_M2FLAGS): Add
	-Wcase-enum.
	* libm2iso/Makefile.in: Regenerate.
	* libm2log/Makefile.am (libm2log_la_M2FLAGS): Add
	-Wcase-enum.
	* libm2log/Makefile.in: Regenerate.
	* libm2pim/Makefile.am (libm2pim_la_M2FLAGS): Add
	-Wcase-enum.
	* libm2pim/Makefile.in: Regenerate.

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