Make Tuleap build compatible centos6

Import Raphaël Hertzog work on setup.sh to make it aware of various platform
flavours (currently centos5, centos6 and debian wheezy).

setup.sh is debian compatible but debian packaging is not yet merged into
stable.

Change-Id: I7dc1dd194c6ef65779f58a1517922081c05c1c0e
Merge commit 'refs/changes/94/394/2' of http://gerrit.tuleap.net/tuleap into tuleap-stable-master

* http://gerrit.tuleap.net/tuleap:
  Make Tuleap build compatible centos6
Tuleap 5.12.99.41