machmode.def: Add BImode.

machmode.def: Add BImode.

        * machmode.def: Add BImode.  Add a column for bitsize.
        * machmode.h (DEF_MACHMODE): Adjust for extra column.
        (GET_MODE_BITSIZE): Use it.
        * rtl.c (DEF_MACHMODE): Adjust for extra column.
        (mode_bitsize): New.
        (mode_mask_array): Use bitsize.
        * combine.c (combine_simplify_rtx): Require inner and outer
        modes to match on nonzero_bits optimizations.

From-SVN: r36501