HOWTO: Use pythia 6xx in ROOT

Root's TPythia6 interface allows the user to run pythia only simulations within root.  By default, root will load a given version of the pythia library.  At present it is version 6.4.16.  In order to run other versions of the library, one must load them by hand before creating an instance of the TPythia6 class. Below is an example for how to download, compile and install
$ wget
$ cvs co pams/gen
$ mkdir pams/gen/pythia6319
$ mv pythia6319.f pams/gen/pythia6319/pythia6319.F # note capitalization
$ cons

$ root4star
[0] .L .sl53_gcc432/lib/
[1] TPythia6 *pythia6 = new TPythia6();
[2] pythia6 -> Pyinit( "FIXT", "p", "p", 38.8 ); // or your favorite configration

TPythia6's author did something very very very bad. As a consequence, the GetParticle(i)
method (defined in TGenerator) returns a pointer to TMCParticle, not the TParticle pointer which one would expect from the documentation in the base class.