Normalize deadman timer's args on U64/F64.  Internals remain the
same.  Modify mesh to collect and output enhanced CPU metrics.

Integrated as a ctor-time option to LLDeadmanTimer and have mesh
use this mode for the stats I'm gathering.

Timer interface violated my design rules and I paid for it
with clumsiness and silent errors.  Cleaned it up mainly
removing the evil default values.  Found better integration
points in the mesh downloader and it's producing fairly
consistent numbers on the MeshTest2 test region (about
5500 downloads, ~90 seconds, +/- 10 seconds).  Will review
with davep and do an early timer stop on teleport which
invalidates a timing sequence.

the deadman's timer.  Found some bugs, dig some cleanup and
documented a few things.  Definitely want to get rid of the
U64/F64 interfaces at sometime but this is a good start.

Will be used for mesh, inventory, etc., operation markers.