vppinfra: add basic rbtree

Algorithm from CLRS, Introduction to Algorithms 3rd Edition, Ch. 13

Change-Id: I5bc2c507593770939cd5584f21dacf36ebd2b4c1
Signed-off-by: Florin Coras <fcoras@cisco.com>
diff --git a/src/vppinfra/CMakeLists.txt b/src/vppinfra/CMakeLists.txt
index df5ca5d..702f6fd 100644
--- a/src/vppinfra/CMakeLists.txt
+++ b/src/vppinfra/CMakeLists.txt
@@ -63,6 +63,7 @@
   random.c
   random_buffer.c
   random_isaac.c
+  rbtree.c
   serialize.c
   slist.c
   socket.c
@@ -146,6 +147,7 @@
   random_buffer.h
   random.h
   random_isaac.h
+  rbtree.h
   serialize.h
   sha2.h
   slist.h