get the SVN poller working, use the real archive name (with revision in it), get...

get the SVN poller working, use the real archive name (with revision in it), get the pthread builder download the archive instead of updating the svn. Still todo: update ucontext builder, automatic trigger of real builders once the distmaker is done. Afterward, any autogenerated can be droped from svn

git-svn-id: svn+ssh://scm.gforge.inria.fr/svn/simgrid/simgrid/trunk@6022 48e7efb5-ca39-0410-a469-dd3cf9ba447f