PGcommonFunctions.pl - Common mathematical functions used in PG problems.
This macro provides common mathematics functions (exponential, log, trig and combinatoric).
Either call Parser (if it has been loaded) or the functions below. (If it's ever the case that both the Parser and PGauxiliaryFunctions.pl are both preloaded, then there will be no need for this, as you can always use the Parser versions. We only need this because Parser might not be loaded.)