Pimcore_Tool_Console::exec() timeout support: check for support of the --kill-after flag as some linux distributions still ship with very old versions of  gnutools (eg. CentOS)

git-svn-id: http://www.pimcore.org/svn/pimcore/private/core/trunk@4789 1f8fe7d8-47f0-464c-8d0a-336f4953ab05