mach-o: read and dump: prebound_dylib, prebind_cksum, twolevel_hints.

mach-o: read and dump: prebound_dylib, prebind_cksum, twolevel_hints.

include/mach-o:
	* external.h (mach_o_prebound_dylib_command_external)
	(mach_o_prebind_cksum_command_external)
	(mach_o_twolevel_hints_command_external): New types.

bfd/
	* mach-o.h (bfd_mach_o_twolevel_hints_command)
	(bfd_mach_o_prebind_cksum_command): New types.
	(bfd_mach_o_prebound_dylib_command): Rewrite.
	(bfd_mach_o_load_command): Add prebind_cksum and twolevel_hints
	fields.
	* mach-o.c (bfd_mach_o_read_prebound_dylib): Read and decode the
	command.
	(bfd_mach_o_read_prebind_cksum): New function.
	(bfd_mach_o_read_twolevel_hints): Ditto.
	(bfd_mach_o_read_command): Handle prebind cksum and twolevel hints
	commands.

binutils/
	* od-macho.c (OPT_TWOLEVEL_HINTS): New macro.
	(options): Add entry for twolevel_hints.
	(dump_data_in_code): Fix error message.
	(dump_twolevel_hints): New function.
	(dump_load_command): Handle prebound dylib, prebind cksum
	and twolevel hints.
	(mach_o_dump): Handle twolevel hints.