cobol: Improve the creation of run-time arrays.

It's often the case that GENERIC creates arrays of values that are passed
to libgcobol routines.  These changes improve how those arrays are created
and initialized with constructors.  The main changes are to establish them
as const and to use current techniques for CONSTRUCTOR creation.

gcc/cobol/ChangeLog:

	* genapi.cc (array_of_long_long): Improved creation.
	(gg_array_of_size_t): Likewise.
	(gg_array_of_field_pointers): Likewise.
	(gg_array_of_uchar_p): Likewise.
	(parser_sort): Use modified routine.
	(parser_file_sort): Likewise.
	(parser_file_merge): Likewise.
	* gengen.cc (gg_array_of_size_t): Improved creation.
	* gengen.h (gg_array_of_field_pointers): Likewise.
	(gg_array_of_size_t): Likewise.