Support the width_bucket function

Support the width_bucket(wbo, wbb1, wbb2, wbc) which returns an integer between 0 and wbc+1 by mapping wbo into the ith equally sized bucket made by dividing wbb1 and wbb2 into equally sized regions. If wbo < wbb1, return 1, if wbo > wbb2 return wbc+1. Reference: SQL standard section 4.4.