Re: ld plugin bfd_make_readable leak

Commit 3097045a18a8 runs into an abort in objalloc_free_block when the
memory being bfd_release'd wasn't bfd_alloc'd.  Fix that.

	* coffgen.c (_bfd_coff_free_cached_info): Don't release
	raw_syments when obj_coff_keep_raw_syms.
	* libcoff-in.h (obj_coff_keep_raw_syms): Define.
	(struct coff_tdata): Add keep_raw_syms.
	* peicode.h (pe_ILF_build_a_bfd): Set obj_coff_keep_raw_syms.
	* libcoff.h: Regenerate.