Make the plain nginx version the same as nginx-ssl.
In a further change we will replace nginx by a dummy package,
depending on +nginx-ssl instead. This allows a smooth upgrade.

For nginx-util leave the ssl and the ssl-nopcre versions only.
For nginx-mod-luci remove the duplicate ssl version.
Replace the removed packages by dummies for a smooth upgrade.
The dummy packages will be removed after a transition period.

Additionally, enable the http2 module for nginx-ssl by default
and cleanup the nginx.init file.

Signed-off-by: Peter Stadler <peter.stadler@student.uibk.ac.at>

* fix regex capture (to conform std)
* fix issues for Clang/libcxx (warnings/includes)
* fix CONFLICTS in the Makefile
* use /bin/sh in host scripts and shellcheck them
* add callback for setting arguments in ubus::call

Signed-off-by: Peter Stadler <peter.stadler@student.uibk.ac.at>

Add tests for nginx-ssl-util and nginx-ssl-util-nopcre using (fake)chroot.
Clean the code up making nginx-ssl-util a header file.
Both changes are for better (future) code quality only.

There are minor functional improvements:
* fix compiler error of gcc7 by using std=c++17
* fix error if there is no lan/loopback interface
* notice instead of error message if there is no default server
* add ipv6-prefix-assignment.*.local-address.address for LAN
* add CONFLICTS in Makefile for choosing the right version
* add cast to release of unique_ptr to avoid warning
* add version message to help message

Signed-off-by: Peter Stadler <peter.stadler@student.uibk.ac.at>

* Do not destroy the iterator twice if cur==this (segfault).
* Do not add the delimiter clim=='\0' when creating the SSL directives.
* Set the right SSL_SESSION_CACHE_ARG for nginx-util get_env.
* Remove static from the constexpr that are used only for Line::build.
* Concat strings instead of appending them for not using a non-const ref
(to remove some warnings of clang-tidy -checks=google-runtime-references)

Signed-off-by: Peter Stadler <peter.stadler@student.uibk.ac.at>

This can do the main work of nginx/nginx-ssl init script.
For nginx-ssl it can create selfsigned certificates, too.
It uses libpcre and libopenssl iff nginx(-ssl) uses them.

Signed-off-by: Peter Stadler <peter.stadler@student.uibk.ac.at>