If flag-o-matic treats -O3 as a permitted flag, in UNSTABLE_FLAGS, I would
really appreciate it if the individual components of O3 were also permitted.
In practice, this means -finline-functions, -frename-registers, -fweb as
well as their negations. I would also like to see -ftracer allowed.
That can't be done 100% clean, since different versions of gcc, implies
different "auto" flags for the different -On levels.