A call time f x will evaluate f x as usual, but will also (provided the
report_timing flag is true as it is by default) print the CPU time taken by
that function evaluation.
FAILURE CONDITIONS
Never fails in itself, though it propagates any exception generated by the call
f x itself.
EXAMPLE
# time NUM_REDUCE_CONV `123 EXP 14`;;
CPU time (user): 0.09
val it : thm = |- 123 EXP 14 = 181414317867238075368413196009
USES
Monitoring CPU time taken, e.g. to test different algorithms or implementation
optimizations.