Fixes #2746

Increasing libvarnishapi.so version from 1.0.6 to 2.0.0

Submitted by:	Frederic Lecaille <flecaille@haproxy.com>

Ref: c2888919
     72bacde7
     46f1557d

In other news:  VTEST works.

Fixes: 	#2696

* either NULL or properly named
* only named arguments can be possibly be speficied multiple times
* only named arguments can be optional
* positional arguments could be missing

Fixes #2694

Fixes:	#2745

... argument to specify a custom location

Fixes #2742

Submitted by:	Frederic Lecaille <flecaille@haproxy.com>

Two new paramters allow the limit and than handling (ignore, warn, fail)
to be configured.

Fixes #2713

Fixes: #2603

in order to have it build first and cleaned up

fixes this issue when switching to an older branch:

$ git checkout ...
error: The following untracked working tree files would be overwritten
by checkout:
	bin/varnishtest/vtc_h2_dectbl.h
Please move or remove them before you switch branches.
Aborting

This still lacks error handling and thus is not a fix for #2589, but at
least we're not writing past the end of the workspace any more.