Fixes: #1592

Require that buffer arguments have greater than zero length to allow
for zero termination.

Make sure that NULL buffers are not touched.

what we really want with them.

Now I just need to figure out where to stuff them.

dependent (is there a C-L header ?), and semantic (ie:  HEAD request
doesn't have body, even if the response has C-L etc.)

Spotted by:	Dridi Boukelmoune

Use vcl_synth or vcl_backend_error where appropriate.

until it's been allocated.

This patch delays the VXID allocation until the time we know that we
will actually be logging anything for this request (not completely all
whitespace noise). This keeps the code in one place only (plus the ESI
mock request handling), instead of separated between the linger wait,
cache acceptor and pipelining code paths.

Coincidentally fixes the logging of timestamps problem in #1588.

Test case by daghf.

Fixes: #1581 #1588

This enables catching batch related log problems using logexpect.

This commit will make several test cases start failing until #1588 has been fixed.

healthy backend.

Fixes: #1575