[PATCH v2][gold] Mips: Fix emitting .reginfo section.

[Cary Coutant]

>         * mips.cc (Mips_relobj::Mips_relobj): Initialize
>         has_reginfo_section_.
>         (Mips_relobj::has_reginfo_section_): New data member.
>         (Mips_relobj::has_reginfo_section): New method.
>         (class Mips_output_section_reginfo): Change base class to
>         Output_section_data, and set masks of the output .reginfo section
>         in constructor.
>         (Mips_output_section_reginfo::as_mips_output_section_reginfo):
>         Remove.
>         (Mips_output_section_reginfo::set_masks): Likewise.
>         (Mips_output_section_reginfo::set_final_data_size): Likewise.
>         (Mips_output_section_reginfo::do_print_to_mapfile): New method.
>         (Target_mips::do_make_output_section): Remove.
>         (Mips_relobj::do_read_symbols): Set has_reginfo_section_ to true
>         if the object contains a .reginfo section.
>         (Target_mips::do_finalize_sections): Create a .reginfo output
>         section if needed.

I've committed this on your behalf.

Thanks!

-cary