(Theory: "stty raw" doesn't clear -echo)

I came for something else, but one thing led to another...

Emit a proper summary at the top, but elide ENUMs to keep it
compact.

If the entire VCL prototype fits in the header, put it there.
else if it fits with ENUMs elided do that or finally resort
to just the name + "(...)".

If the header didn't hold the full prototype, emit a codeblock
with it, and split that in one line per argument if it is too
wide for the manual pages.

Remove the manual summary from the libvmod_blob docs.

otherwise summarize it (ie: elide ENUMs)

And sync bin/varnishd/Makefile.am to use the same (and more accurate)
variable name.

Spotted by Reza.

generated VCL synopsis:

old:	new OBJ = VOID dyn(STRING addr, STRING port)
new:	new OBJ = dyn(STRING addr, STRING port)

Spotted by:	simon

Ref: aa8875a4
Ref: c310f04b

Fixes 2461

Fixes #2386

I don't think it matters anywhere else, but future-proofing is good.

Hopefully fixes #2586

This should help readability of the code, hopefully.

The API remains unchanged.

Local variables for vsl_status are called 'r', variables holding
a VSLQ_dispatch_f return value are called 'i'