Improve the shmlog facilities.

Improve the shmlog facilities.

Move the sleeping and timing out into the library so we do not
have to repeat it in all apps.  Should we ever find an app
that needs something else, we will cater for it then.

Add VSL_Dispatch() which calls a (supplied) function (pointer) for each
record.  Additional useful information is passed as arguments, such
as classification (backend/client/other) etc.

Add a default handler for printing a record.

Add VSL_Select() where the application can specify tags that are mandatory
and which should not be subject to -i/-x/-I/-X/-b/-c filtering.

Be more frugal with memory.

git-svn-id: svn+ssh://projects.linpro.no/svn/varnish/trunk@817 d4fa192b-c00b-0410-8231-f00ffab90ce4