remove virtual specification from LHCb::Track member functions
remove use of deprecated (and removed in C++17)
std::{unary,binary}_function
remove unneccessary include of stdio.h and functional
change functors to be non-template classes (structs) with a
templated operator() -- this avoids having to specify a type
when instantiating an instance of a functor
remove commented out old code
avoid unneccessary statics
simplify Track::addToStates implementation -- no need to reserve
first, do not modify the argument
optimize Track::copy -- skip resetting data to zero when it will
subsequently be overwritten