* configure.in (ENUM_BITFIELDS_ARE_UNSIGNED): Added.  Check that
        bitfields of the host compiler are not signed quantities.
        * config.in: Regenerate.
        * configure: Regenerate.
        * system.h (USE_ENUM_BITFIELDS): Added.
        (ENUM_BITFIELDS): Added.
        * rtl.h (rtx_def): Members `code', `mode', now ENUM_BITFIELD.
        (SHORT_ENUM_BUG): Deleted.
        * tree.h (tree_common): Members `code', `mode', `built_in_class',
        now ENUM_BITFIELD.
        * config/i386/xm-sco.h (ONLY_INT_FIELDS): Deleted.
        (CODE_FIELD_BUG): Likewise.
        * config/m68k/x-apollo68 (CC): Deleted SHORT_ENUM_BUG.
        (OLD_CC): Likewise.
        * config/m68k/x-ccur (X_CFLAGS): Likewise.

From-SVN: r33233