PR binutils/17552, binutils/17533
* bucomm.c (is_valid_archive_path): New function. Returns false
for absolute pathnames and pathnames that include /../.
* bucomm.h (is_valid_archive_path): Add prototype.
* ar.c (extract_file): Use new function to check for valid
pathnames when extracting files from an archive.
* objcopy.c (copy_archive): Likewise.
* doc/binutils.texi: Update documentation to mention the
limitation on pathname of archive members.