mach-o: handle lasz load dylib command.

bfd/
	* mach-o.c (bfd_mach_o_read_dylib): Handle lazy load dylib.
	(bfd_mach_o_read_command): Ditto.

binutils/
	* od-macho.c (dump_load_command): Handle lazy load dylib.
od-macho: dump compact unwind info.

binutils/
	* od-macho.c (dump_section_header): Renames of dump_section.
	(dump_segment): Adjust after renaming.
	(OPT_COMPACT_UNWIND): Define.
	(options): Add compact unwind.
	(mach_o_help): Document compact_unwind.
	(unwind_x86_64_regs, unwind_x86_regs): New arrays.
	(dump_unwind_encoding_x86, dump_unwind_encoding)
	(dump_obj_compact_unwind, dump_exe_compact_unwind)
	(dump_section_content): New functions.
	(mach_o_dump): Handle compact unwind.

include/mach-o/
	* unwind.h: New file.