vmodtool python running in the wrong locale may complain about an
invalid character

Actually this bit of the README rightfully only applies to pre 5.0

This reverts commit 371122cd.

In tests, use {...} for regexen

This fixes them for current master and also helps readability

- config.h first
- cache.h or (additional) vdef.h before vrt.h

this is required for master since 81bc4cef2a5e651a9e34ae5400672a88663db7ef

this means that Varnish > 5.0.0 must be enforced, since workspace
is not available in init/fini in earlier versions

This reverts commit 79de4cf9.

Will solve this instead by maintaining a 4.1 branch, for versions
not compatible with Varnish < 5.0

We _could_ selectively keep the tests for these functions failing in <5.0,
but looking forward this does seem like wasted effort.

so that README appears in the project front page of a public repo

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.