physics, parser: rewrote statistics handling

It was retarded having to duplicate the variables like progress on the struct array for the threads. Now handle the struct array for every thread from inside a global struct containing shared, single stats. Best of all, phys_stats->bh_new_alloc gives you the total while phys_stats->t_stats[1].bh_new_alloc gives you only the new allocations for thread 1. And also the whole thing is exposed to Lua. And it's even easier there. t_stats.bh_new_alloc is the total while t_stats[1].bh_new_alloc is the thread specific stat. It's good and I like it.