New setting some functions and files for Placement

2014-05-14, Wednesday
I new added place_parallel.h/c for try_place_using_multi_threads(),
this function will call try_place_parallel(). For next days, I will
add parallel_path_delay.h/c for computing timing_cost and delay_cost.
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I new added Makefile modified vpr_types.h
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I had modified block_types_t member. I appended the _TYPE suffix to
all member variables. And I changed clb_t** clb to clb_t** clb_grids.