[plt-scheme] 299.25

The exp-tagged code in CVS for MzScheme and MrEd is now version 299.25.

Changes:

 * Revised the definition of "character" to include the code points
   #xFFFE and #xFFFF.

   I previously omitted these two code points due to a misunderstanding
   of Unicode and UTF-8. Now, every Unicode scalar value corresponds to
   a MzScheme character. (A Unicode scalar value is a code point that
   is not in the surrogate range #xD800 to #xDFFF. The code points
   #xFFFE and #xFFFF are not supposed to show up in strings that are
   traded between programs, but that's just a convention; the
   prohibition is not part of the definition of "code point", "scalar
   value", or UTF-8.)

 * Removed optional argument of `continuation-mark-set->list' (which
   previously exposed unmarked frames).

 * Fixed a `syntax-recertify' bug that affected mzc compilation with
   contracts (reported here by David Van Horn).

 * Added `draw-bitmap-section-smooth' method to bitmap-dc% (not dc<%>).
   This method scales a bitmap more nicely than `draw-bitmap-section'
   into a scaled dc<%> (at least for most platforms and scales), but
   it's also much slower.

Matthew