Several string comparisons could never yield true because they had an 'x' guard
added to the variable but not to the constant value. Fix that by guarding both sides.


scripts/make_win_bin_dist:
  Fix bug#27833 "Bourne shell string comparison issue in scripts/make_win_bin_dist":
  
  Several string comparisons could never yield true because they had an 'x' guard
  added to the variable but not to the constant value. Fix that by guarding both sides.
  
  Use this occasion to apply some corrections to the comments and the usage text.
  
  Also, ensure the ".pdb" file is always optional.