also enable by default thread support for linuxicc.

git-svn-id: http://root.cern.ch/svn/root/trunk@4578 27541ba8-7e3a-0410-8455-c3a389f83636

configure

@@ -569,7 +569,7 @@ fi
 # Check for posix thread library
 #
 case $platform in
-linux|linuxdeb)
+linux|linuxdeb|linuxicc|linuxecc)
     if test "x$enable_thread" = "x"; then
         enable_thread="yes"
     fi