build-sys: allow tests run parallel

Signed-off-by: Sami Kerola <kerolasa@iki.fi>
build-sys: update .gitignore files

Signed-off-by: Sami Kerola <kerolasa@iki.fi>
docs: thanks to Cheer Xiao this software has IPv6 support

The prof. Xing Li in Tsinghua University, with LI Zimu, asked Cheer to
make the dhcpd-pools more usable for them which I, as a project
maintainer, could not be more pleased.  Whils making the IPv6 analysis to
work Cheer also fixed various other issues.  Kudos to him, and big thanks
to everyone.

CC: Xing Li <xing@cernet.edu.cn>
CC: LI Zimu <lzm@cernet.edu.cn>
CC: Cheer Xiao <xiaqqaix@gmail.com>
Signed-off-by: Sami Kerola <kerolasa@iki.fi>
tests: fix make distcheck

It is best to make dhcpd-pools used from PATH, which makes out of tree
build check to work.

Signed-off-by: Sami Kerola <kerolasa@iki.fi>
docs: fix doxygen make distcheck breakage

The docs directory needs to be handled properly, e.g., create Makefile
which nothing, when doxygen is not enabled.

Signed-off-by: Sami Kerola <kerolasa@iki.fi>
release: 2.21

Signed-off-by: Sami Kerola <kerolasa@iki.fi>
tests: add complete check including multiple ranges and shared networks

Signed-off-by: Sami Kerola <kerolasa@iki.fi>
include: add missing declarations to dhcpd-pool.h

This will fix eight warnings similar to the example below.

sort.c:104:5: warning: no previous declaration for 'comp_ip' [-Wmissing-declarations]

Signed-off-by: Sami Kerola <kerolasa@iki.fi>
cppcheck: fix variable scoping

[src/dhcpd-pools.c:68]: (style) The scope of the variable 'c' can be reduced.
[src/getdata.c:210]: (style) The scope of the variable 'c' can be reduced.
[src/hash.c:102]: (style) The scope of the variable 'l' can be reduced.

Signed-off-by: Sami Kerola <kerolasa@iki.fi>
build-sys: update .gitignore

Signed-off-by: Sami Kerola <kerolasa@iki.fi>
getdata: treat binding states abandoned, expired and release like free