Remove use of Time Stamp Counter (rdtsc)

[gcongiu]

The Time Stamp Counter was once an excellent high-resolution, low-overhead way for a program to get CPU timing
information. With the advent of multi-core CPUs, systems with multiple CPUs, and hibernating operating systems, the
TSC cannot be relied upon to provide accurate results — unless great care is taken to correct the possible flaws: 
rate of tick and whether all cores (processors) have identical values in their time-keeping registers.

-- https://en.wikipedia.org/wiki/Time_Stamp_Counter