Clean up time handling code

Clean up time handling code

base/str.hh:
    this should really be inline
base/time.cc:
base/time.hh:
    clean up how the time class works.  Export only one, and let
    people calculate their own elapsed times, etc.
sim/main.cc:
    sim/sim_time.X -> base/time.X

--HG--
rename : sim/sim_time.cc => base/time.cc
rename : sim/sim_time.hh => base/time.hh
extra : convert_revision : f3888fe3a1fdd1022084c282b58407c631a6d9a0