[Bugfix] ANSI standard allows CL:SETF symbol follows to #'(.

Since a list (setf foo) is a valid function name, following format is a
valid input to READer:

  #'(setf foo)

The extended #' reader macro offered by PAPPLY falsely assumes that only
CL:LAMBDA (and some extension introduced by each implementation) is
allowed after #'(. In other words, above form was read as (p setf foo).
This bug is fixed.