* gdbserver/linux-low.c (usr_store_inferior_registers): Support
        registers which are allowed to fail to store.
        * gdbserver/linux-low.h (linux_target_ops): Likewise.
        * gdbserver/linux-ppc-low.c (ppc_regmap): Support FPSCR.
        (ppc_cannot_store_register): FPSCR may not be storable.
        * regformats/reg-ppc.dat: Support FPSCR.