request #7457: fix security vulnerability

Prevent bash injection via headers on viewvc

Change-Id: I9002bef7a7c2f645609acb652b710e40de852732
Merge commit 'refs/changes/31/3031/2' of ssh://gerrit.tuleap.net:29418/tuleap into stable

* ssh://gerrit.tuleap.net:29418/tuleap:
  request #7457: fix security vulnerability
This is Tuleap 7.5.99.6

Change-Id: I53c286364c9f9973f768740d93a166eb495f4350