Since gnulib commit 6954995d unistd.h is included via stdlib.h
on BSD systems, which requires config.h to be included first.

Add config.h to the files that use it.

Part of this commit reverts commit 6ee918deSigned-off-by: NJán Tomko <jtomko@redhat.com>
Reviewed-by: NErik Skultety <eskultet@redhat.com>

Lead by example in examples/
Signed-off-by: NJán Tomko <jtomko@redhat.com>
Reviewed-by: NErik Skultety <eskultet@redhat.com>

For instance:

hellolibvirt/hellolibvirt.c: In function 'showDomains':
hellolibvirt/hellolibvirt.c:100:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (i = 0; i < numNames; i++) {
                   ^
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>

Some of the examples make use of asprintf and strtol functions (to keep
things simple) which are prohibited to use within our code (enforced by
syntax-check). Therefore besides adding some examples, this patch also updates
cfg.mk to exclude examples directory from asprintf and strtol rules, as well as
updates .gitignore to exclude all the new admin binaries created in the
'examples' dir.
Signed-off-by: NErik Skultety <eskultet@redhat.com>