Move bfd_elf_bfd_from_remote_memory to opncls.c

Move bfd_elf_bfd_from_remote_memory to opncls.c

bfd_elf_bfd_from_remote_memory is just a wrapper, and the function
could be implemented for other formats.  Move it to opncls.c because
it acts a little like some of the other bfd_open* routines.  Also give
it the usual FUNCTION etc. comment so prototypes and docs are handled
automatically.

	* elf.c (bfd_elf_bfd_from_remote_memory): Move to..
	* opncls.c: ..here, add FUNCTION comment.
	* bfd-in.h (bfd_elf_bfd_from_remote_memory): Delete prototype.
	* bfd-in2.h: Regenerate.