PR modula2/108121 Re-implement overflow detection for constant literals

PR modula2/108121 Re-implement overflow detection for constant literals

This patch fixes the overflow detection for constant literals.
The ZTYPE is changed to int128 (or int64) if int128 is unavailable and
constant literals are built from widest_int.  The widest_int is converted
into the tree type and checked for overflow.
m2expr_interpret_integer and append_m2_digit are removed.

gcc/m2/ChangeLog:

	PR modula2/108121
	* gm2-compiler/M2ALU.mod (Less): Reformatted.
	* gm2-compiler/SymbolTable.mod (DetermineSizeOfConstant): Remove
	from import.
	(ConstantStringExceedsZType): Import.
	(GetConstLitType): Re-implement using ConstantStringExceedsZType.
	* gm2-gcc/m2decl.cc (m2decl_DetermineSizeOfConstant): Remove.
	(m2decl_ConstantStringExceedsZType): New function.
	(m2decl_BuildConstLiteralNumber): Re-implement.
	* gm2-gcc/m2decl.def (DetermineSizeOfConstant): Remove.
	(ConstantStringExceedsZType): New function.
	* gm2-gcc/m2decl.h (m2decl_DetermineSizeOfConstant): Remove.
	(m2decl_ConstantStringExceedsZType): New function.
	* gm2-gcc/m2expr.cc (append_digit): Remove.
	(m2expr_interpret_integer): Remove.
	(append_m2_digit): Remove.
	(m2expr_StrToWideInt): New function.
	(m2expr_interpret_m2_integer): Remove.
	* gm2-gcc/m2expr.def (CheckConstStrZtypeRange): New function.
	* gm2-gcc/m2expr.h (m2expr_StrToWideInt): New function.
	* gm2-gcc/m2type.cc (build_m2_word64_type_node): New function.
	(build_m2_ztype_node): New function.
	(m2type_InitBaseTypes): Call build_m2_ztype_node.
	* gm2-lang.cc (gm2_type_for_size): Re-write using early returns.

gcc/testsuite/ChangeLog:

	PR modula2/108121
	* gm2/pim/fail/largeconst.mod: Increased constant value test
	to fail now that cc1gm2 uses widest_int to represent a ZTYPE.
	* gm2/pim/fail/largeconst2.mod: New test.

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