bug#15233: pp-eval-expression: Signature parity with `eval-expression'

[Jambunathan K <kjambunathan@gmail.com>]

eval-expression takes INSERT-VALUE.  But `pp-eval-expression' doesn't.
But it should.

,----[ C-h f eval-expression RET ]
| eval-expression is an interactive compiled Lisp function in
| `simple.el'.
| 
| It is bound to M-ESC :.
| 
| (eval-expression EXP &optional INSERT-VALUE)
`----

,----[ C-h f pp-eval-expression RET ]
| pp-eval-expression is an interactive autoloaded compiled Lisp function
| in `pp.el'.
| 
| It is bound to M-:.
| 
| (pp-eval-expression EXPRESSION)
| 
| Evaluate EXPRESSION and pretty-print its value.
| Also add the value to the front of the list in the variable `values'.
| 
`----