bin * readelf.c (options): Add "decompress".
(usage): Mention -z/--decompress.
(parse_args): Handle -z.
(uncompress_section_contents): Move to earlier in the file.
(dump_section_as_strings): If requested, decompress the section
before dumping.
(dump_section_as_bytes): Likewise.
* doc/binutils.texi: Document the new option.
tests * binutils-all/z.s: New test. Checks the --decompress option to
readelf.
* binutils-all/readelf.exp: Run the test.
* binutils-all/readelf.z: Expected output from readelf.
