[plt-scheme] 299.19

The exp-tagged code in CVS for MzScheme and MrEd is now version 299.19.

Changes:

 * Fixed character-counting bug for input ports. (This bug was
   introduced in 299.18. It was the main source of the trouble that
   Artem reported in coloring Russian text in DrScheme.)

 * Changed Mac OS X text measuring and rendering. When character
   combining is off, then measuring should be much faster, but
   rendering tends to be slower. Editors draw without combining, and
   they measure text a lot more than they draw it, so faster measuring
   should help more than slower rendering hurts.

 * Added `pipe-content-length'.

 * Added `locale-string-encoding'.

 * Changed `call-with-semaphore[/enable-break]' to accept extra
   arguments for the called function.

Matthew