[plt-scheme] 369.9

MzScheme and MrEd are now version 369.9 in the SVN repository trunk.

The changes in 369.9 are small, but this version also synchronizes many
bug fixes applied in the SVN repository during 369.8.

Changes:

 * Added `procedure-struct-type?', which recognizes descriptors for
   structure types where the instances are applicable as procedures.

 * Added `use-background-style' and `background-style-used?' methods to
   editor-snip%, so that nested editors can be transparent or use a
   specified background color. This change affects the editor-snip
   encoding in the WXME format, so that files saved with embedded
   editors in v369.9 cannot be read in earlier versions.

 * When the first phase of `module' expansion categorizes a top-level
   forms as an expression (as opposed to a definition, `require',
   etc.), then the form's expansion is completed in the second phase in
   an expression context.

   For example,

    (module d mzscheme
     (def g)
     (define-syntax def
       (syntax-rules ()
         [(_ id) (define id 5)])))

   now triggers a syntax error, because `(def g)' is categorized as an
   expression before the `def' macro is encountered.

 * Inside MzScheme: added `XFORM_START_SKIP', etc., macros for working
   around code fragments that `mzc --xform' cannot handle.

Matthew