Few files were affected. The release scripts was updated.

Given that some OSes have bash in /usr/local/bin and in order not to
give too easy an excuse to Olivier for not backporting fixes, let's
make a few scripts rely on /usr/bin/env bash instead of /bin/bash :-)

The changelog is empty when creating a dev0 version and this confuses
the commit message, let's clearly mention the exact copy when there are
no changes.

create-release shows the next steps at the end and suggest to use
"git push origin master" but on my machine it's not "origin" so let's
determine it using git config and only use origin as a fall back.

The following example files awere removed as irrelevant by this
time :
  auth.cfg check.conf ssl.cfg haproxy.spec

The following scripts were removed as having been unused for more
than a decade :
  debug2ansi debug2html debugfind check init.haproxy stats_haproxy.sh

seemless_reload.txt was moved to doc/ where it's more suitable.

haproxy.vim was moved to contrib/syntax-highlight/

scripts/create-release was updated not to try to update haproxy.spec
anymore.

The README was barely usable after all the additions having accumulated
over the years. This patch introduces a new INSTALL file explaining how
to build and install haproxy with various levels of details. The README
is now mostly an index to the list of useful documentations.

If it's not set, fall back to git config --get.

Some versions of tail don't accept "tail +4".

The stats page proudly displays "Updates (v1.5)". This version is inherited
from version.h which has not been updated since 1.5, so let's teach the
create-release script about it.

This must be backported to 1.7. 1.6 now uses the same script (externally)
for the release and will automatically benefit from it.

These ones have been used for several months already and are quite
convenient to emit new releases and backport fixes. I'm fed up with
having different versions on different machines, let's commit them
now.