sbitmap cleanups

[Jeffrey A Law]

  In message < 10004101850.AA29628@vlsi1.ultra.nyu.edu >you write:
  >     Err, we have functions to dump sbitmaps and vectors of sbitmaps.  What
  >     does your debugging function do that those do not?
  > 
  >     See dump_sbitmap, dump_sbitmap_vector
  > 
  > (1) They write to the file specified in their operand and you can't
  > always get "stderr" passed as a parameter in GDB.
So make them default to stdout or stderr if NULL is passed as the file
pointer.  Or put a wrapper around them that passes stdout/stderr.


  > (2) They dump the bitmap as a string of bits while the new function shows
  > which are nonzero.
OK.  This makes sense for some uses.  The stream of bits makes sense when
looking at dataflow problems :-)

jeff