Force a clean pull-and-build of Tcl/Tk on Windows buildbots.

diff --cc Tools/buildbot/external-common.bat
index 48004a720ebaac93b765c2d5e3747013ffa8ee1a,1e973969b5b42ab197060a2015f67e9d29715c80..ae00d3e3e2febb1f29734db345be2c747bfc6e63
--- 1/Tools/buildbot/external-common.bat
--- 2/Tools/buildbot/external-common.bat
+++ b/Tools/buildbot/external-common.bat
@@@ -5,17 -5,25 +5,25 @@@ cd .
  @rem XXX: If you need to force the buildbots to start from a fresh environment, uncomment
  @rem the following, check it in, then check it out, comment it out, then check it back in.
  @rem if exist bzip2-1.0.6 rd /s/q bzip2-1.0.6
- @rem if exist tcltk rd /s/q tcltk
- @rem if exist tcltk64 rd /s/q tcltk64
- @rem if exist tcl8.4.12 rd /s/q tcl8.4.12
- @rem if exist tcl8.4.16 rd /s/q tcl8.4.16
- @rem if exist tcl-8.4.18.1 rd /s/q tcl-8.4.18.1
- @rem if exist tk8.4.12 rd /s/q tk8.4.12
- @rem if exist tk8.4.16 rd /s/q tk8.4.16
- @rem if exist tk-8.4.18.1 rd /s/q tk-8.4.18.1
+ if exist tcltk rd /s/q tcltk
+ if exist tcltk64 rd /s/q tcltk64
+ if exist tcl8.4.12 rd /s/q tcl8.4.12
+ if exist tcl8.4.16 rd /s/q tcl8.4.16
+ if exist tcl-8.4.18.1 rd /s/q tcl-8.4.18.1
+ if exist tcl-8.5.2.1 rd /s/q tcl-8.5.2.1
+ if exist tcl-8.5.9.0 rd /s/q tcl-8.5.9.0
+ if exist tcl-8.5.11.0 rd /s/q tcl-8.5.11.0
+ if exist tcl-8.6.1.0 rd /s/q tcl-8.6.1.0
+ if exist tk8.4.12 rd /s/q tk8.4.12
+ if exist tk8.4.16 rd /s/q tk8.4.16
+ if exist tk-8.4.18.1 rd /s/q tk-8.4.18.1
+ if exist tk-8.5.2.0 rd /s/q tk-8.5.2.0
+ if exist tk-8.5.9.0 rd /s/q tk-8.5.9.0
+ if exist tk-8.5.11.0 rd /s/q tk-8.5.11.0
+ if exist tk-8.6.1.0 rd /s/q tk-8.6.1.0
  @rem if exist db-4.4.20 rd /s/q db-4.4.20
  @rem if exist openssl-1.0.1e rd /s/q openssl-1.0.1g
 -@rem if exist sqlite-3.7.12 rd /s/q sqlite-3.7.12    
 +@rem if exist sqlite-3.7.12 rd /s/q sqlite-3.7.12
  
  @rem bzip
  if not exist bzip2-1.0.6 (