SHT_RELR sh_link and sh_info

SHT_RELR sh_link and sh_info

I don't think it makes any sense for a SHT_RELR section to specify a
symbol table with sh_link.  SHT_RELR relocations don't use symbols.
There is no real need to specify sh_info either, SHT_RELR is not for
relocatable object files.  Anyway, fuzzers of course don't restrict
themselves to even half-sensible objects.  So they found a hole in
objcopy using a non-alloc SHT_RELR in an ET_EXEC.  In that case BFD
set up the SHT_RELR section as if it were a SHT_REL against the
sh_info target section.  When it came to reading in the target section
relocs, the count was horribly wrong which caused a buffer overflow.

	* elf.c (bfd_section_from_shdr <SHT_RELR>): Always just make a
	normal section, don't treat it as a reloc section.