No longer works so is just crufting up the code

functions. CPU_TPS is now only found in one Makefile.am and one
file, clocks.c.

Many of the uses are commented out or protected by TIMER_VERBOSE.
TIMER_VERBOSE no longer compiles, so these changes are untested
and just aim to guide the future...

Limit the time-step size such that the smoothing length does not change by more than a pre-defined constant.