configure.ac: Set ld_vers_major, ld_vers_minor and ld_vers_patch for GNU linker.

        * configure.ac: Set ld_vers_major, ld_vers_minor and ld_vers_patch for
        GNU linker. Support linker version x.x.x.x.x. Require GNU linker
        20050308/2.16.0 or newer for comdat group.
        * configure: Regenerated.
        * config.in: Regenerated.
        * varasm.c (default_function_rodata_section): Put .rodata section in
        COMDAT group when necessary.
        (default_elf_asm_named_section): Rename HAVE_GAS_COMDAT_GROUP to
        HAVE_COMDAT_GROUP.
        (default_unique_section_1): Don't use .gnu.linkonce when COMDAT is
        available.

Co-Authored-By: H.J. Lu <hongjiu.lu@intel.com>
Co-Authored-By: Paul Brook <paul@codesourcery.com>

From-SVN: r99395