PR modula2/109032 - message 'compiler checks to force' is too complicated

Correct typos and improve the descriptions of command line options.
Improve comments in gm2-gcc/m2expr.cc.

gcc/m2/ChangeLog:

	PR modula2/109032
	* gm2-gcc/m2expr.cc: Correct ? : order in comments.
	(m2expr_BuildDivM2): Improve comment.
	* lang.opt: Improve option descriptions.

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