On many busy production systems, the VSL buffer for transactions often
fills up, triggering a flush to the VSM. If such a transaction takes a
long time, it can happen that the flushed data is overwritten before
the whole transaction completes. The result is that these transactions
are missed by varnishncsa and other tools. Increasing the vsl_buffer
does the trick, at some cost in workspace usage.

The cost implies that one should increase the workspaces, too. Since
the old defaults of 64k each are too low for many common use cases
today, it is natural to increse everything in one patch.

Some test cases have been updated. These are all cases where the
workspaces have been set very low, and to make sure we are still
testing the same regression, the vsl_buffer has been set to the old
default instead of increasing the workspace.