PR modula2/109496 Fix constant char parameter passing to an array of char

PR modula2/109496 Fix constant char parameter passing to an array of char

This patch fixes PR modula2/109496 and PR modula2/109497.  The fix for
PR modula2/109496 promotes a char constant to a string.  The PR
modula2/109497 allows for constant chars to be added to form a string.
The fixes for both PR's occur in M2GenGCC.mod and M2GCCDeclare.mod
after the resolving of constant declarations.

gcc/m2/ChangeLog:

	* gm2-compiler/M2ALU.def (PopChar): New procedure function.
	* gm2-compiler/M2ALU.mod (PopChar): New procedure function.
	* gm2-compiler/M2GCCDeclare.mod (PromoteToString): Detect
	a single constant char and build a C string.
	* gm2-compiler/M2GenGCC.mod (IsConstStr): New procedure
	function.
	(GetStr): New procedure function.
	(FoldAdd): Use IsConstStr.
	* gm2-compiler/M2Quads.mod: Formatting changes.
	* gm2-gcc/m2expr.cc (m2expr_GetCstInteger): New function.
	* gm2-gcc/m2expr.def (GetCstInteger): New procedure function.
	* gm2-gcc/m2expr.h (m2expr_GetCstInteger): New prototype.

gcc/testsuite/ChangeLog:

	PR modula2/109497
	* gm2/pim/run/pass/addcharconst.mod: New test.
	PR modula2/109496
	* gm2/pim/run/pass/singlechar.mod: New test.

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