The few hpack development tools are now integrated into the main
makefile, which allows to remove the original one which was causing
lots of build warnings. A README was added to explain how to build
instead.
The makefile was not suited anymore as it didn't consider all
required compiler options and was causing way too many build
warnings with modern compilers. Let's just remove it and indicate
that this has to be built from the top of the project.
The following directories were moved from contrib/ to dev/ to make their
use case a bit clearer. In short, only developers are expected to ever
go there. The makefile was updated to build and clean from these ones.
base64/ flags/ hpack/ plug_qdisc/ poll/ tcploop/ trace/
