_Version_ or _version_: PLT software online version checking
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The version collection allows online version checking of PLT software.
The user-side software sends version information about installed
software to a server that compares that information against the latest
released versions.

In particular, the user-side software sends to the server

 - the binary version as reported by (version), a MzScheme primitive,
   and
 - the values of the release-version and release-iteration fields in
   the info.ss file for collections, if those fields exist

If the binary version is out of date, that information is reported to
the user.  Otherwise, the status of each package is reported.  The
determination of whether a package is up-to-date is made on the server
side.

Two files may be used to run version checks from MrEd and MzScheme:
_check-text.ss_ for (MrEd or MzScheme), and _check-gui.ss_ (for MrEd).
These files contain modules that export a procedure named
check-version:

 (require (lib "check-gui.ss" "version"))

and

 (require (lib "check-text.ss" "version"))

For check-text.ss, the procedure is called with

> (check-version)

For check-gui.ss, the procedure is called with

> (check-version [frame] [sync?])

where the optional argument `frame' is either a frame% instance or #f,
the default.  The optional `sync?' argument is any Scheme value, #f by
default.  If `sync?' is #f, the procedure returns immediately;
otherwise, it returns after the user clicks OK on the dialog box that
appears (or when an error occurs).
