[plt-scheme] 299.13

The v299-tagged code in CVS for MzScheme and MrEd is now version 299.13.

This is an incomplete release, because it's taking me a while to get
module security right. But the current implementation is a good
stopping point, and it's past time to bring everyone up to speed.
I'll follow up with a terribly long message about module security.

Changes:

 * X: MrEd widgets look better, at least to me.

 * Added 'no-border flag to editor-canvas%.

 * Added optional port-name arguments to `make-pipe' and
   `open-{input,output}-{string,bytes}'.

 * Unix and Mac OS X: path expansion removes redundant slashes.

 * Added `protect' sub-form of `provide' (see next message).

 * Added `current-code-inspector' (see next message).

 * Added certification of contexts for unexported identifiers (see next
   message).

 * Added `syntax-recertify', `syntax-recertify-constrained?', and
   `syntax-extend-certificate-context', but they don't yet work right
   (see next message).

 * Added `namespace-reprotect-module' (see next message).

 * Changed `module->namespace' and module re-definition so that they're
   controlled by the code inspector, not the modules attach state (see
   next message).

The docs have not yet been updated.

Matthew