Calling functions like recv() with a NULL buffer is not explicitly
allowed by the POSIX standard, so it must be avoided to be portable
across different libc implementations. Allocate an initial buffer before
handling requests, and also pass this buffer to the peek recv() call.

Fixes: 531937cf ("gluon-neighbour-info: fix broken output with large results")

This removes PKG_VERSION and PKG_RELEASE from most Makefiles, as the
value was never useful for Gluon packages; instead, PKG_VERSION is set
to 1 in gluon.mk.

It also removes two other weird definitions:

- gluon-iptables-clamp-mss-to-pmtu replicating the old PKG_VERSION logic
  from gluon-core, but without the fixed PKG_BUILD_DIR to prevent
  unnessary rebuilds
- gluon-hoodselector set GLUON_VERSION=3

Currently a buffer with a fixed size of 8192 bytes is used. However the
result can potentially be larger, which leads to a truncated JSON
output on stdout. UDP packets, without compression and with IP
fragmentation, can be up to 64KiB large.

Instead of using a fixed size buffer on the stack ask the kernel first
about the size of the UDP data and allocate a buffer of appropriate size
on the heap before receiving the UDP data.

The issue was observed with a custom respondd provider.

Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>

End the process after one result in case -l is not given
and destination address is unicast.
Reduces singleshot execution time from timeout seconds to around 150ms.

resolves #2184

inet_pton() doesn't set errno on regular parse errors, so using perror()
doesn't make sense (and we avoid a confusing "Success" message).

We also make use of the boolean support of simple-uci to make scripts
clearer.

gluon-neighbour-info: improve verbosity on wrong cli parameters

Avoid commiting configs inbetween to decrease number of flash writes.

Fixes #714.

If the query was via multicast, the response isn't matched by
--state ESTABLISHED,RELATED

This fixes #619

The timeout was calculated incorrectly (in each iteration the span between
the start time and the current time was substracted from the timeout
again), and would often become negative, causing warnings in the kernel
log.

sse-multiplex likes to get the header as fast as possible.

error() is a glibc specific function and should not be used in
code meant to be portable.

This is a simple client for gluon-announced.