Log Message:
lang/tcl: Upgrade from version 8.4.18 to 8.5.12

Highlights of Tcl 8.5
  * Features: 8.5 has over 90 TIPs included to provide a wide variety of
     new features.
  * Bignums: Tcl now supports arbitrary-precision integers, which improves
    math operations on large integers.
  * Safer interps: Tcl's powerful safe interpreter mechanism now has
    improved control of time and command limits in slave interpreters.
  * clock command: More robust implementation of command for specifying
    time, with significant l10n and i18n improvements.
  * dict command: New data structure that allows access to data by value
    rather than a variable name, which is substantially faster.
  * Additional improvements: Faster list search, new and improved
    mathematics procedures, anonymous procedures, new ways to package Tcl
    extensions, Tcl-level custom channel types, file and line location
    information for each command, and more.

There is of course much, much more.
See [8.5 Changes](http://wiki.tcl.tk/10630) on the wiki for a complete
list of new features.