Continuing work to convert the hppa targets to multiarch partil.

    Continuing work to convert the hppa targets to multiarch partil.

        * hppa-tdep.c: Add some missing forward declarations.
        (frameless_function_invocation): Prefix the function name
        by "hppa_" to avoid polluting the namespace.  Update all calls
        to use the new function name.
        (saved_pc_after_call): Ditto.
        (init_extra_frame_info): Ditto.
        (frame_chain): Ditto.
        (push_dummy_frame): Ditto.
        (target_read_pc): Ditto.
        (target_write_pc): Ditto.
        (in_solib_call_trampoline): Ditto.
        (in_solib_return_trampoline): Ditto.
        (skip_trampoline_code): Ditto.
        (hppa_read_fp): New function, renamed from target_read_fp.
        (hppa_target_read_fp): New function, using hppa_read_fp.
        This function conforms to the function profile for the
        READ_FP gdbarch method.
        (hppa_extract_struct_value_address): New function, extracted
        from the definition of the DEPRECATED_EXTRACT_STRUCT_VALUE_ADDRESS
        macro.
        (hppa_frame_num_args): New function.
        (hppa_gdbarch_init): Setup the gdbarch vector for the hppa target.

        * config/pa/tm-hppa.h: Wrap around all gdbarch-eligible macros
        inside "#if !GDB_MULTI_ARCH ... #endif" conditional, in preparation
        for the switch to multiarch partial.
        Update some of the macros definitions to match some changes
        described above in the name of the function they are calling.
        (PUSH_DUMMY_FRAME): Add a FIXME explaining why this macro will
        not be straightforward to convert. Do now wrap it inside
        "#if !... #endif" to remember that this macro has still not
        been taken care of.
        (FIX_CALL_DUMMY): Likewise.