The RDTSC frequency reported by CPUID is not accurate to its true frequency.
We will spawn a separate thread to calculate the true RDTSC frequency after a measurement period of 30 seconds has elapsed.
This formats all copyright comments according to SPDX formatting guidelines.
Additionally, this resolves the remaining GPLv2 only licensed files by relicensing them to GPLv2.0-or-later.
From -fsanitize=address, this code wasn't calling the proper destructor.
Adding virtual destructors for each inherited class and the base class
fixes this bug.
While we are at it, mark the functions as final.