refactor usage of compressed_debug_section_type

refactor usage of compressed_debug_section_type

bfd/ChangeLog:

	* bfd-in.h (bfd_hash_set_default_size): Add COMPRESS_UNKNOWN
	  enum value.
	(struct compressed_type_tuple): New.
	* bfd-in2.h (bfd_hash_set_default_size): Regenerate.
	(struct compressed_type_tuple): Likewise.
	* libbfd.c (ARRAY_SIZE): New macro.
	(bfd_get_compression_algorithm): New function.
	(bfd_get_compression_algorithm_name): Likewise.

gas/ChangeLog:

	* as.c: Do not special-case, use the new functions.

ld/ChangeLog:

	* emultempl/elf.em: Do not special-case, use the new functions.
	* lexsup.c (elf_static_list_options): Likewise.