More work on vcl4.1 reserved words etc.

In vcl 4.1 symbol names are unique across all types & kinds.

We want it to be very explicit when non-default VCL versions
are used in test-cases.

For now, the only case this adds is a missing leading zero in the
day of the month of RFC822/RFC1123 - style http dates as in

		Fri, 2 Mar 2018 14:26:02 GMT (bad)
instead of	Fri, 02 Mar 2018 14:26:02 GMT (correct)

This is clearly invalid according to
https://tools.ietf.org/html/rfc7231#section-7.1.1.2
yet accepted by other webserver software.

because the messages in the reference version were horrible.

Also don't rely on protocol numbers, they vary per platform.

having bereq.body hardcoded in the compiler is not nice.

Previously, we would get PROXY vxids without a Proxy line like:

    262253 Begin          c sess 0 PROXY
    262253 SessOpen       c w.x.y.z 1234 a0 a.b.c.d 85 1516787007.682753 32
    262253 Link           c req 262254 rxreq