Initial cleanup pass of lisa's function call tracking

Initial cleanup pass of lisa's function call tracking
code.

base/statistics.hh:
    We're getting rid of FS_MEASURE, but for now, we're going
    to still use a compile time flag to turn on and off binning
    of statistics.  (The flag is STATS_BINNING)
cpu/exec_context.cc:
cpu/exec_context.hh:
kern/tru64/tru64_system.cc:
    get rid of FS_MEASURE
cpu/simple_cpu/simple_cpu.cc:
    yank the function call tracking code out of the cpu and move
    it into the software context class itself.
kern/tru64/tru64_system.hh:
    get rid of FS_MEASURE
    move all of the tacking stuff to the same place.
sim/system.hh:
    cleanup

--HG--
extra : convert_revision : 73d3843afe1b3ba0d5445421c39c1148d3f4e7c0