- make struct VSL_data the uniform handle.
- eliminate global variables (this allows a program to have multiple
  shmlogs open at the same time).
- add a VSL_Delete() to clean up

This breaks libvarnishapi compatibility with the 2.x series.






git-svn-id: http://www.varnish-cache.org/svn/trunk/varnish-cache@4775 d4fa192b-c00b-0410-8231-f00ffab90ce4