cherry picked from https://github.com/ansible/ansible/pull/6899

Fixes #9991

hacking/env-setup now adds the configured library path in ANSIBLE_CONFIG
to the ANSIBLE_LIBRARY environment variable in addition to the previous
default of ANSIBLE_HOME/library.

This replaces #5950.

This fixes issue #5026. It used to work. The regression was
introduced in 2b3381de.

Signed-off-by: martin f. krafft <madduck@madduck.net>

This replaces double conditional brackets with single ones and gets ris
of bashisms, so that the tool should be sourcable from any POSIX shell.

Constructs like [ $foo = "$bar"* ] yield filesystem-globbing behaviour
according to POSIX. A compliant way is to use case statements.

Signed-off-by: martin f. krafft <madduck@madduck.net>

In case paths contain spaces, it's better to consistently quote
variables, and to use $() instead of `` for external invocations.

Signed-off-by: martin f. krafft <madduck@madduck.net>

dirname/basename do not need an external process, shell variable
expansion can be made to do the same a bit faster.

Signed-off-by: martin f. krafft <madduck@madduck.net>

The env-setup script is not intended to be run directly, so it does not
need a shebang line, which might even create the wrong expectations.

Signed-off-by: martin f. krafft <madduck@madduck.net>

'source' is actually a "bashism" and the POSIX-way of sourcing a file
uses the single dot (which is arguably less readable). Both yield the
same result, and since the script may now also be sourced from
within the hacking directory, this commit expands the usage synopsis
accordingly.

Signed-off-by: martin f. krafft <madduck@madduck.net>

Conflicts:
	hacking/env-setup

Bash needs a special case to determine the dirname of the sourced path
(the hacking dir), but in all other cases, using $0 allows the script to
be sourced also from within the hacking directory, not only from its
parent.

Signed-off-by: martin f. krafft <madduck@madduck.net>

env-setup now takes a -q argument to run in quiet mode

independent of output, and can also see all the output nicely grouped together if we want
to reformat it or make summaries of statistics.

environment (ANSIBLE_{LIBRARY,HOSTS}) if defined.

Update manpages to represent this.

Also update the env-setup script to set ANSIBLE_{LIBRARY,HOSTS}.