vcl/ldp: add locked sessions shim layer

Moves LDP logic that allows sharing of sessions between multi-process
app workers into a separate VCL shim layer. Also refactors LDP to use
the new layer.

Change-Id: I8198b51eae7d099a8c486e36b29e3a0cb8cee8e9
Signed-off-by: Florin Coras <fcoras@cisco.com>
diff --git a/src/vcl/CMakeLists.txt b/src/vcl/CMakeLists.txt
index abe1bf0..cbf954f 100644
--- a/src/vcl/CMakeLists.txt
+++ b/src/vcl/CMakeLists.txt
@@ -20,6 +20,7 @@
   vcl_bapi.c
   vcl_cfg.c
   vcl_private.c
+  vcl_locked.c
 
   LINK_LIBRARIES
   vppinfra svm vlibmemoryclient rt pthread
@@ -43,6 +44,7 @@
   ldp_glibc_socket.h
   vcl_test.h
   vppcom.h
+  vcl_locked.h
   ldp_socket_wrapper.h
 )