pe_ILF_object_p and bfd_check_format_matches

pe_ILF_object_p and bfd_check_format_matches

If pe_ILF_object_p succeeds, pe_ILF_build_a_bfd will have changed the
bfd from being file backed to in-memory.  This can have unfortunate
results for targets checked by bfd_check_format_matches after that
point as they will be matching against the created in-memory image
rather than the file.  bfd_preserve_restore also has a problem if it
flips the BFD_IN_MEMORY flag, because the flag affects iostream
meaning and should be set if using _bfd_memory_iovec.  To fix these
problems, save and restore iostream and iovec along with flags, and
modify bfd_reinit to make the bfd file backed again.  Restoring the
iovec and iostream allows the hack in bfd_reinit keeping BFD_IN_MEMORY
(part of BFD_FLAGS_SAVED) to be removed.
One more detail: If restoring from file backed to in-memory then the
bfd needs to be forcibly removed from the cache lru list, since after
the bfd becomes in-memory a bfd_close will delete the bfd's memory
leaving the lru list pointing into freed memory.

	* cache.c (bfd_cache_init): Clear BFD_CLOSED_BY_CACHE here..
	(bfd_cache_lookup_worker): ..rather than here.
	(bfd_cache_close): Comment.
	* format.c (struct bfd_preserve): Add iovec and iostream fields.
	(bfd_preserve_save): Save them..
	(bfd_preserve_restore): ..and restore them, calling
	bfd_cache_close if the iovec differs.
	(bfd_reinit): Add preserve param.  If the bfd has been flipped
	to in-memory, reopen the file.  Restore flags.
	* peicode.h (pe_ILF_cleanup): New function.
	(pe_ILF_object_p): Return it.
	* bfd.c (BFD_FLAGS_SAVED): Delete.
	* bfd-in2.h: Regenerate.