Initial work to support out-of-tree builds
```
./autogen.sh
mkdir build
cd build
../configure
make
make check
```
IMPORTANT: `autogen.sh` doesn't call `configure` automatically anymore!!
You have to do: `./autogen.sh && ./configure --$OPTIONS`.
A little bit annoying but the pattern `autogen && configure && make` is
very common on Linux.
Known issues:
* `make doc` doesn't work in out-of-tree builds, yet
* Windows/MinGW/DPDK (out-of-tree) builds have not been tested, so it is unlikely they work
See: #2992
Extend internal unit tests to handle multiple configurations.
As some examples, add tests about:
* disabling some protocols
* disabling Ookla aggressiveness
Every configurations data is stored in a dedicated directory under
`tests\cfgs`
This fixes some build/test issues resulting when using tarballs.
* nDPI uses autotools (especially autoconf) in a wrong way, see #1163
Signed-off-by: lns <matzeton@googlemail.com>
