updated planet/scribble docs

collects/planet/planet.scrbl

@@ -873,13 +873,36 @@ in Scribble documentation.
              #:module-paths (mod-suffix-id ...) maybe-sources pre-flow ...))]
 @defform[(defmodulereader*/no-declare/this-package (suffix-id ...+)
            maybe-sources pre-flow ...)]
+@defform[(declare-exporting/this-package suffix-id ... maybe-sources)]
 )]{
 
-Variants of @racket[defmodule], etc., from @racketmodname[scribble/manual] in
-which each module path is replaced by an identifier (@racket[suffix-id] or
-@racket[mod-suffix-id]) representing a module within the current version of the
-containing @|PLaneT| package.
+Variants of @racket[racketmod], @racket[racketmodname],
+@racket[racketmodlink], @racket[defmodule], @racket[defmodulereader],
+@racket[defmodulelang], @racket[defmodule*], @racket[defmodulelang*],
+@racket[defmodulereader*], @racket[defmodule*/no-declare],
+@racket[defmodulelang*/no-declare],
+@racket[defmodulereader*/no-declare], and @racket[declare-exporting],
+respectively, that implicitly refer to the PLaneT package that
+contains the enclosing module.
 
+The full module name passed to @racket[defmodule], etc is formed by
+appending the @racket[suffix-id] or @racket[mod-suffix-id] to the
+symbol returned by @racket[(this-package-version-symbol)], separated
+by a @litchar{/} character, and tagging the resulting symbol as a
+@racket[planet] module path. As a special case, if @racket[suffix-id]
+is @racketid[main], the suffix is omitted.
+
+For example, within a package named @tt{package.plt} by @tt{author},
+version @tt{1:0}, the following are equivalent:
+@racketblock[
+(defmodule/this-package dir/file)
+  @#,elem{=} (defmodule (planet author/package:1:0/dir/file))
+]
+and
+@racketblock[
+(defmodule/this-package main)
+  @#,elem{=} (defmodule (planet author/package:1:0))
+]
 }
 
 @subsection{Terse Status Updates}