vmodtool doesn't generate them automatically (at least not up to
Varnish 4.1)

This reverts commit c47dcc40.

This was only set for encoders, but the contract for encoders in
vmod_blobcode.h does not require setting errno, and it isn't
necessary, since insufficient space is the only cause for
encoders to fail (callers don't check errno, and don't need to).

- it's implicit that the description is the description and we got
  no other subsections but the example

- the prototype is generated by vmodtool already

Update examples to reflect the new defaults

Add vtc to test all examples from the documentation

I've just changed varnishtest to be fine with whitespace and comments

This reverts commit 2915adac.

Patch from Nils Goroll

Patch by Nils Goroll

Patch from Nils

we hit the null terminator for a string in a STRING_LIST

Patch by Nils

special case where the encoding and decoding are the same

Patch by Nils Goroll <nils.goroll@uplex.de>