cobol: Repair mh_identical MOVEs involving DEBUG registers [PR126277]

The mh_identical MOVE routine was flummoxed by the DEBUG-XXX registers that
are children of DEBUG-ITEM.  These changes repair that problem.

	PR cobol/126277

gcc/cobol/ChangeLog:

	* move.cc (mh_identical): Handle externals that have parents.
	(mh_binary_to_packed): Eliminate trailing whitespace.
	* symbols.cc (symbol_table_init): Correct attributes of DEBUG-CONTENTS.

libgcobol/ChangeLog:

	* constants.cc (struct cblc_field_t): Adjust initialization of
	DEBUG-ITEM fields.