Remove duplicate constants created between passes

Remove duplicate constants created between passes

There is no need to re-create constant literals between passes.
This patch creates a constant pool and reuses a constant literal
providing it is created at the same location.  This in turn avoids
generating duplicate overflow error messages when encountering an
out of range constant literal.

gcc/m2/ChangeLog:

	* gm2-compiler/SymbolTable.mod (ConstLitPoolEntry): New
	pointer to record.
	(ConstLitSym): New field RangeError.
	(ConstLitPoolTree): New SymbolTree representing name to
	index.
	(ConstLitArray): New dynamic array containing pointers
	to a ConstLitPoolEntry.
	(CreateConstLit): New procedure function.
	(LookupConstLitPoolEntry): New procedure function.
	(AddConstLitPoolEntry): New procedure function.
	(MakeConstLit): Re-implemented to check the constant lit
	pool before calling CreateConstLit.
	* m2.flex: Add ability to decode binary constant literals.

gcc/testsuite/ChangeLog:

	* gm2/pim/run/pass/constlitbase.mod: New test.

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