Merge with 3.4

Tools/buildbot/external-common.bat

@@ -9,6 +9,7 @@ cd ..
 @rem if exist tcltk64 rd /s/q tcltk64
 @rem if exist tcl-8.6.1.0 rd /s/q tcl-8.6.1.0
 @rem if exist tk-8.6.1.0 rd /s/q tk-8.6.1.0
+@rem if exist tix-8.4.3.4 rd /s/q tix-8.4.3.4
 @rem if exist db-4.4.20 rd /s/q db-4.4.20
 @rem if exist openssl-1.0.1h rd /s/q openssl-1.0.1h
 @rem if exist sqlite-3.7.12 rd /s/q sqlite-3.7.12