Newlines at EOFs.
Add examples for the rest of built-in pict constructors
slideshow/balloon: fix `balloon` to match docs
correcting the type signature docs for htdp-intermediate's compose.
added show-derivations to redex
adjust the language dialog so that clicking on the example
the corresponding #lang line.
improve the language dialog a little bit:
- make clicking on the example languages
  select the 'The Racket Language' radio button
- when the clicked example language matches
  the buffer, have a more friendly message
enabling shared in plai with some shameless copying of kernel code
whoops, forgot to add this file in my last commit
fix the draw contract (and change some one-of/c's to or/c's)
Some more `#lang racket' -> `#lang racket/base' conversions

(And some other related minor racketisms.)
`#lang racket' -> `#lang racket/base' conversions in drracket and in redex.
`#lang racket' -> `#lang racket/base' conversions in plot and in images.
`#lang racket' -> `#lang racket/base' conversions in demodularizer.
`#lang racket' -> `#lang racket/base' conversions in future-visualizer.
`#lang racket' -> `#lang racket/base' conversions in net/websocket.
`#lang racket' -> `#lang racket/base' conversions in stepper.
`#lang racket' -> `#lang racket/base' conversions in frtime.
add ad hoc optimization of `car' to `unsafe-car', etc.

In `(if (pair? x) E1 E2)', convert `(car x)' in E1 to
`(unsafe-car x)', and similarly for `(cdr x)'. Also,
`(begin (car x) (cdr x))' converts to `(begin (car x)
(unsafe-cdr x))' since `(car x)' implies a `pair?' test
on `x'.
flatten simple `define-values' within a module

This flattening is useful for the definition of `assq', for example.