Some clean up work with faults.

Some clean up work with faults.

arch/alpha/faults.cc:
    Renamed the _stat stat to a more descriptive _count, got rid of some old commented out code, and moved common fault handling code, ie recording that the fault happend and that it wasn't mispeculated, into the FaultBase class.
arch/alpha/faults.hh:
    Renamed the _stat stat to the more descriptive _count, and renamed the appropriate accessor functions.
kern/kernel_stats.cc:
kern/kernel_stats.hh:
    The fault statistics are now handled by the fault classes themselves.
sim/faults.cc:
    The default implementation of the "invoke" method now does what all faults should do first, ie record that the fault happened, and make sure the fault isn't being executed on a mispeculated execution path.
sim/faults.hh:
    There is now a default implementation of invoke, and the stat function is taken care of in the architecture specific fault classes.

--HG--
extra : convert_revision : f6656fbea991df9addf85cad740ac37b1036b71a