Don't run new orphan tests on i860 and i960

Don't run new orphan tests on i860 and i960

These targets use the generic ELF support, so don't handle orphans
well.  The patch also updates the orphan doco to reflect this fact,
and deletes some ELF details that don't really add anything.

	* ld.texinfo (Orphan Sections): Mention that not all targets
	handle orphans well.  Delete ELF details.
	* testsuite/ld-elf/orphan-9.d: Don't run for i860 and i960.
	* testsuite/ld-elf/orphan-10.d: Likewise.