Fix types for eq/eqv/equal-hash-code

Thanks to this SO question:
  http://stackoverflow.com/questions/26130215
racket/gui Cocoa: disable App Nap; switch to GUI mode more lazily

On 10.9 and later, `racket/gui` now disables App Nap. Otherwise, a
program like

 #lang racket/base
 (require racket/class
          racket/gui/base)

 (define T 0.05)

 (let loop ([prev (current-inexact-milliseconds)])
   (sleep T)
   (define now (current-inexact-milliseconds))
   (define delta (- now prev))
   (when (delta . > . (* 2000 T))
     (printf "long wait ~a at ~a\n" delta now))
   (loop now))

will start to report a wait of more than 10 seconds, as App Nap
puts the process to sleep.

Relatedly, when `racket/gui` is started via plain `racket` (as opposed
to GRacket), then it starts in "accessory" mode instead of "regular"
mode, which means that the application does not appear in the dock
or have a menu bar. As soon as a frame is shown or a root menu bar
is created, the application is promoted to "regular" mode. This works
in 10.7 and later.
JIT: fix allocation of `letrec`-bound closure over unboxed flonums

The closure could be allocated as uninitialized memory with the
expectation that it would be filled right away, but boxing values
to put in the closure could expose the uninitialized memory to
the GC. Fix the problem by boxing before allocating closures.
fix some random generators broken when refactoring things to improve contract-stronger?
Remove dependence on libgtkgl; fix indirect rendering problem

The right way to render to pixmaps is to create a GLX pixmap wrapper
and render to *that*. Almost nobody does this - including libgtkgl -
and it's almost never a problem. But it causes crashes on my system
in indirect rendering mode.

This commit changes three things.

 1. OpenGL on Linux no longer requires libgtkgl, only libGL, which
    comes preinstalled on many (most? almost all?) systems.

 2. Rendering to pixmaps is done properly, via a GLX pixmap wrapper.

 3. Direct rendering is done whenever possible, even for pixmaps.
Added warning about GLX choosing indirect rendering
Add Fogus's slides.
Racket-y
more Rackety, useless exn msg
racket/network: improve UDP support

Generalize `udp-send-to`, etc., to try each possibility of
a resolved address (instead of just the first one) like
`udp-connect!` does. This matters, for example, when using
"localhost" as an address, when the machine resolves "locahost"
to both "127.0.0.1" and "::1", and when the socket is created
for the second one that would be tried.

Also, detect and discard asynchronous ICMP errors.
racket/gui Cocoa: fix test for 10.9
John's slides.
Only ask for multisampling of GLX 1.4 or higher; make getting context atomic
remove tests that combine outline mode with
pixel checking, as the behavior doesn't seem to be
guaranteed

also, rackety
remove 'print' mode from the Pretty Big language

it was buggy and fixing the bug makes it identical to write
mode, so instead of that, lets just make there not be a print mode

also, minor edits and Rackety
fix a bug that disabled check syntax's tooltips

bug was introduced in august 2013
add author and toc
add support for macro-specified tooltips to check syntax
remove equality to make the program easier to read

(in consultation with Jay)
new unix bitmaps for redex tests to sate drdr

thanks, Jay