core: fixes for gcc's '-pedantic' flag build

* warnings on 'void *' arguments
* warnings on empty initializations
* warnings on empty array (array[0])

Change-Id: Iae440f54cbd59580eb69f3ecaed5a9926c0edf95
BUG: 875913
Signed-off-by: Avra Sengupta <asengupt@redhat.com>
Reviewed-on: http://review.gluster.org/4219
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Anand Avati <avati@redhat.com>