expose variables for number of global events per simulated second,

expose variables for number of global events per simulated second,
millisecond, microsecond, etc. so that the user can explicitly
convert between system ticks and time and know what sorts of
expensive operations are being used for that conversion.

arch/alpha/alpha_tru64_process.cc:
arch/alpha/pseudo_inst.cc:
dev/etherdump.cc:
dev/etherlink.cc:
dev/ns_gige.cc:
dev/sinic.cc:
dev/tsunami_io.cc:
dev/uart.cc:
sim/stat_control.cc:
sim/syscall_emul.hh:
    Use the new variables for getting the event clock
dev/etherdump.hh:
    delete variables that are no longer needed.

--HG--
extra : convert_revision : d95fc7d44909443e1b7952a24ef822ef051c7cf2