implement scribble/srcdoc' via submodules instead of expand'

Also add a `for-doc' require form, make `proc-doc' et al. provide
forms, make `provide/doc' an alias for `provide'.

original commit: 964020f288a73340052b471327bfe873d804eea8

collects/framework/gui-utils.rkt

@@ -3,7 +3,7 @@
 (require string-constants racket/gui/base
          racket/contract/base racket/class)
 (require scribble/srcdoc)
-(require/doc scheme/base scribble/manual)
+(require/doc racket/base scribble/manual)
 
 (define (trim-string str size)
   (let ([str-size (string-length str)])

collects/framework/main.rkt

@@ -28,7 +28,7 @@
                        framework/decorated-editor-snip
                        framework/private/decorated-editor-snip))
 
-(require/doc scheme/base scribble/manual framework/private/mapdesc)
+(require (for-doc scheme/base scribble/manual framework/private/mapdesc))
 
 (provide-signature-elements
  (prefix application: framework:application-class^)
@@ -62,7 +62,7 @@
   (export framework^)
   (link standard-mred@ framework@))
 
-(provide/doc
+(provide
 
  (proc-doc
   color:get-parenthesis-colors-table 

collects/framework/preferences.rkt

@@ -344,8 +344,8 @@ the state transitions / contracts are:
   @{See also @racket[preferences:set-default].
         
         @racket[preferences:get] returns the value for the preference
-        @racket[symbol]. It raises
-        @index['("exn:unknown-preference")]{@racket[exn:unknown-preference]}
+        @racket[symbol]. It raises an exception matching
+        @racket[exn:unknown-preference?]
         if the preference's default has not been set.})
 
  (proc-doc/names
@@ -357,8 +357,8 @@ the state transitions / contracts are:
     users requests a change to a preference.
     
     @racket[preferences:set] immediately writes the preference value to disk.    
-    It raises
-    @index['("exn:unknown-preference")]{@racket[exn:unknown-preference]}
+    It raises an exception matching
+    @racket[exn:unknown-preference?]
     if the preference's default has not been set.
     
     See also @racket[preferences:set-default].})
@@ -391,9 +391,8 @@ the state transitions / contracts are:
     unmarshalling functions by calling
     @racket[preferences:set-un/marshall] before adding a callback.
     
-    This function raises
-    @index['("exn:unknown-preference")]{@racket[exn:unknown-preference]}
-    @racket[exn:unknown-preference]
+    This function raises an exception matching
+    @racket[exn:unknown-preference?]
     if the preference has not been set.})
  (proc-doc/names
   preferences:set-default

collects/framework/test.rkt

@@ -6,6 +6,7 @@
          scribble/srcdoc
          (for-syntax racket/base)
          (prefix-in :: framework/private/focus-table))
+(generate-delayed-documents) ; enables for-doc--for-label import of `framework'
 (require/doc scheme/base scribble/manual
              (for-label framework))