Update place.c and place_parallel.c

1) I found that placer_opts_t was a constant struct, so I changed
paramter in try_swap. I change placer_opts_t placer_opts to const
placer_opts_t placer_opts;

2) I new added a function descript main placement stage in try_place()
void run_main_placement(...);

3) new update place_paralle.c
Change all functions in place.c to static funcions

Due to some terrible data structures differences between vpr4.3
and vpr5.0.2, Now I modified the functions in place.c from global
to static.