,cd for Racket REPL

It's not perfect and undocumented, but useful nonetheless.
Highlighting [else properly in Racket buffers

That is, `else' gets keyword fontlocking.  Undecided as to whether
extend this highlighting to all schemes...
Racket: indentation for all 'for' forms

We had only for two of them, and one was wrong!
Support for user-defined Guile info nodes

In my debian machine, the info nodes for guile live in the "guile-2.0"
node, rather than plain "guile".  A new customizable variable,
geiser-guile-manual-lookup-nodes, lets now specify additional names,
and we only add indexes to the info-lookup mode definition when the
node actually exists.
Correctly buttonizing paths with leading spaces in DBG buffers

Just adjusting a regexp.
Racket: fix for module compilation for recent rackets

This one probably requires Racket 5.3, and incorporates some
parameterization to the module compilation and evaluation code in
Geiser's version of enter.rkt.  I'm mostly mirroring what the latter
does, and i'm probably not completely understanding all corner cases,
so the two users of Geiser should keep an eye open for possible
breakage introduced by this patch.
[WIP] Draw images inline in the Racket REPL.

On the racket side, we use a custom print handler to print
images (convertible? values; see file/convertible) in a special format:
#<Image: filename>

On the geiser side, we add a comint post-output hook to search for
that filename and replace it with inline images.
[WIP] Emacs cleans up temp. images, and a parameter controls whether or not they are displayed in the REPL.
[WIP] Add capability for images to be viewed in an external image viewer.
Documentation improvements
Simplified image display.

Emacs now remembers the directory that Racket put the last image in.
It leaves up to 10 previously viewed images in this directory,
providing an 'image history'.

This also reduces memory requirements; emacs no longer reads image
content into memory.
Racket: configurable image cache directory

Brought to you by a comma-command in the REPL and the REPL startup
function.
Racket: reading into elisp-land the cache dir as needed

When no cache dir is set in the emacs customization, we ask Racket for
the one that it's using by default.
racket: reading into elisp-land the cache dir as needed

When no cache dir is set in the emacs customization, we ask Racket for
the one that it's using by default.
Merge branch 'master' of git.sv.gnu.org:/srv/git/geiser

Conflicts:
	elisp/geiser-racket.el
Little cleanups
Image display functionality refactored to its own module
Image support: buttons and auto-display in the REPL

When geiser-repl-inline-images-p is false (or we're in a terminal),
the inserted text replacement is a button that calls the external
viewer on click.  There's also a parameter controlling whether the
viewer should be invoked automatically upon insertion.
Credits in header
Racket: fix for enter!