Move freeing of topbuild later to prevent use-after-free
Use system Python3 interpreter

I don't have Python 3.1, but I do have Python 3.3.5 which should suffice.
Clean up for 4.0 syntax.
HTTP is an abbreviation
Update copyright
Move vcl_var.rst, use sane variable name for fp.

Generated RST file should live in include/ like the others, not in reference/.

Try to make the code slightly more readable through a descriptive variable name
for the file handle.
Discover failure to execute varnishd faster
Track source changes