replace singly linked-list Data structure with red-black tree for serverRequest

replace singly linked-list Data structure with red-black tree for serverRequest

Since every data structure used in stack is singly linked-list,
it would be quite inefficient for some data which can be stored massively
like received request info on server.
So I replaced it with red-black tree.
(tree.h from openBSD : http://openbsd.su/src/sys/sys/tree.h)

Change-Id: I68a9b7d00f7f1f9f6aecacee04e0627b72a4ff6b
Signed-off-by: Jaewook Jung <jw0213.jung@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/11443
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Jaehong Jo <jaehong.jo@samsung.com>
Reviewed-by: Ashok Babu Channa <ashok.channa@samsung.com>