Use thread local storage for thread index

This patch deprecates stack-based thread identification,
Also removes requirement that thread stacks are adjacent.

Finally, possibly annoying for some folks, it renames
all occurences of cpu_index and cpu_number with thread
index. Using word "cpu" is misleading here as thread can
be migrated ti different CPU, and also it is not related
to linux cpu index.

Change-Id: I68cdaf661e701d2336fc953dcb9978d10a70f7c1
Signed-off-by: Damjan Marion <damarion@cisco.com>
diff --git a/src/vnet/udp/udp_input.c b/src/vnet/udp/udp_input.c
index 4b22109..810278e 100644
--- a/src/vnet/udp/udp_input.c
+++ b/src/vnet/udp/udp_input.c
@@ -70,7 +70,7 @@
   udp4_uri_input_next_t next_index;
   udp_uri_main_t *um = vnet_get_udp_main ();
   session_manager_main_t *smm = vnet_get_session_manager_main ();
-  u32 my_thread_index = vm->cpu_index;
+  u32 my_thread_index = vm->thread_index;
   u8 my_enqueue_epoch;
   u32 *session_indices_to_enqueue;
   static u32 serial_number;