dont truncate the last character

when called below in

	if (ua_prepend[i])
		appnd(w, space, ua_prepend[i], l);

appnd would exand such that only the first line (l = strlen(r))
was conditional on ua_prepend[i] being non-null, which then would
trigger a null pointer dereference in strncpy.

This is a particularly embarassing bug.

- when missing to hit the tested entry and the returned entry
  contains negative matches, add these to the test string

- improve output

* Pull in varnish version autoconf logic from libvmod-querystring
  Thanks to Dridi Boukelmoune <dridi.boukelmoune@gmail.com>

* Move allocation of memory for dcs_match to caller

* generate dcs_match_mem.h defining DCS_MATCH_MEM_SZ which is the memory size
  required by dcs_match

* move gen* perl and c source to the gen directory to avoid issues with
  make check and recursive subdirs

* first changes to make splint happier

The common_subkey logic depends on this. Before this commit, if an
entry only had common and negative subkeys, it never got registered
as a condidate and dcs_state_remove_candidate could fail an assertion.

avoid unnecessary downloads and rebuilds
improve handling of download errors
make 'make load' work

completely (with up to UA_LIMIT characters)

Add a regression test with a 1025 byte long User-Agent Header

Fixes Assertion `w > uabuf' failed panics.

dcs.type_class will now return one of

	new value	old value
	---------	---------
	desktop		dsk
	smartphone	mob
	tablet		tab