* libhppa.h (pa_arch): Add pa20.

    * libhppa.h (pa_arch): Add pa20.
        (hppa_reloc_field_selector_type): Add R_HPPA_NSEL.
        (e_nsel): Undefine.  Add to hppa_reloc_field_selector_type_alt.
        (hppa_field_adjust): Handle e_nsel.
        * som.c: Provide default definitions for many new relocs found only
        in hpux10 include files.
        (som_fixup_formats): Add several new relocs from hpux10.
        (som_hppa_howto_table): Add hpux10 relocs.
        (som_write_fixups): Handle R_N0SEL and R_N1SEL hpux10 relocs.
Quick stab at handling some of the new hpux10 features.