rtl-simple gets confused if the operator is a branch node

[Aki Helin]

owl says
  > ((if 1 + -) 1 1)
  rtl-simple: unknown thing: #(branch 0 #(value 1) #(value False) #(value #<->) #(value #<+>))

instead of
  > ((if 1 + -) 1 1)
  2

[Aki Helin (aoh)]

was fixed r126, forgot to close.