move the slideshow/pict library to its own collection

also, adjust all of the requires in the tree to point to the pict
collection

original commit: 9932ef33f77ab8bd9751568b4ef2d1b1e3cf4254

collects/scribblings/scribble/class-diagrams.rkt

@@ -1,7 +1,7 @@
 #lang racket/base
 (require (prefix-in etc: mzlib/etc)
          texpict/mrpict
-         (only-in slideshow/pict pin-line pin-arrow-line)
+         (only-in pict pin-line pin-arrow-line)
          (except-in texpict/utils pin-line pin-arrow-line)
          racket/class
          racket/runtime-path

collects/scribblings/scribble/how-to-paper.scrbl

@@ -1,8 +1,8 @@
 #lang scribble/doc
 @(require scribble/manual scribble/bnf "utils.rkt"
-          slideshow/pict
+          pict
           (for-label scriblib/figure scribble/base scribble/sigplan
-                     (except-in slideshow/pict table)))
+                     (except-in pict table)))
 
 @(define-syntax-rule (samplemod . text) (codeblock . text))
 @(define-syntax-rule (sample a . text)
@@ -645,12 +645,12 @@ renders as
 @section[#:tag "pictures"]{Pictures}
 
 Any value that is convertable to an image can be used directly within
-a Scribble document. Functions from the @racketmodname[slideshow/pict]
+a Scribble document. Functions from the @racketmodname[pict]
 and @racketmodname[2htdp/image] libraries, for example, generate
 images. For example,
 
 @sample|{
-  @(require slideshow/pict)
+  @(require pict)
 
   This cookie has lost its chocolate chips: 
   @(colorize (filled-ellipse 40 40) "beige").

collects/scribblings/scribble/struct-hierarchy.rkt

@@ -1,7 +1,7 @@
 #lang racket/base
 
 (require "class-diagrams.rkt"
-         (only-in slideshow/pict pin-arrow-line)
+         (only-in pict pin-arrow-line)
          texpict/mrpict
          (except-in texpict/utils pin-arrow-line)
          racket/system