Fix build fallout with machine_mode changes.

2014-10-29  Ramana Radhakrishnan  <ramana.radhakrishnan@arm.com>

        * config/arm/arm.h (MACHMODE): Treat machine_mode as a
        scalar typedef.
        (CUMULATIVE_ARGS): Guard against target includes.
        (machine_function): Likewise.

From-SVN: r216855