Calibration for each benchmark can be specified on a per board basis.

A calibration file can be specified in the config directory, which is
used at compile time to specify the per benchmark scaling factor.

    * configure.ac: Test whether a calibration file is present. If so,
        report which benchmarks are uncalibrated.
    * doc/beebs.info: Updated documentation to mention calibration, and
        the changed REPEAT_FACTOR
    * doc/beebs.texi: Updated documentation to mention calibration, and
        the changed REPEAT_FACTOR
    * include/support.h: Change REPEAT_FACTOR to BOARD_REPEAT_FACTOR and
        add new definition of REPEAT_FACTOR
    * src/common.mk.am: Grep through the calibration file to find the
        number needed, and add this to the CFLAGS for this benchmark.

    * src/*/Makefile.in: Regenerated
    * config.h.in: Regenerated
    * configure: Regenerated