[patch] sanity check bfd_is_section_compressed header

[DJ Delorie]

> Hmmm, the linker shouldn't even be looking for "ZLIB" unless the
> section name is ".zdebug_str" (or, for the new gABI feature, unless
> the SHF_COMPRESSED flag is set). Wouldn't that be a better check?

I see no reference to SHF_COMPRESSED in the bfd sources, so I can't
check for it.

It seems intentional that it supports both .debug and .zdebug:

2010-10-29  H.J. Lu  <hongjiu.lu@intel.com>
	    Cary Coutant  <ccoutant@google.com>

	* elf.c (_bfd_elf_make_section_from_shdr): Call
	bfd_is_section_compressed to check if a DWARF debug section is
	compressed.  Call bfd_init_section_compress_status or
	bfd_init_section_decompress_status if needed.

  /* Compress/decompress DWARF debug sections with names: .debug_* and
     .zdebug_*, after the section flags is set.  */
  if ((flags & SEC_DEBUGGING)
      && ((name[1] == 'd' && name[6] == '_')
	  || (name[1] == 'z' && name[7] == '_')))
    {