Implement TTL adjustment from VCL

Implement TTL adjustment from VCL

Log in shmem where the TTL came from (doc-candidate):

	696613561 RFC 900 1153517009 1153517014 1153517914 900 0
        |         |   |   |          |          |          |   |
        |         |   |   |          |          |          |   age
        |         |   |   |          |          |          max-age
        |         |   |   |          |          Expires: header
        |         |   |   |          Date: header
        |         |   |   "now"
        |         |   TTL relative to "now"
        |         who set the TTL
        xid of object

or

	696613561 VCL 20 1153517009
	|         |   |  |
	|         |   |  "now"
	|         |   TTL relative to "now"
	|         who set the TTL
        xid of object

git-svn-id: svn+ssh://projects.linpro.no/svn/varnish/trunk@551 d4fa192b-c00b-0410-8231-f00ffab90ce4