api: enable binary API event logging in vat

Cleaned up a few instances of side-bet elog_string hash table
usage. Elog_string handles that problem itself.

Add cli commands to vat to initialize, enable/disable, and save an
event log.

Event logging at the same time in both vpp and vat yields a pair
of event logs which can be merged by the "test_elog" tool.

Type: refactor

Change-Id: I8d6a72206f2309c967ea1630077fba31aef47f93
Signed-off-by: Dave Barach <dave@barachs.net>
diff --git a/src/vlibmemory/memory_shared.c b/src/vlibmemory/memory_shared.c
index fa99369..f44ab7c 100644
--- a/src/vlibmemory/memory_shared.c
+++ b/src/vlibmemory/memory_shared.c
@@ -29,6 +29,7 @@
 #include <vppinfra/format.h>
 #include <vppinfra/byte_order.h>
 #include <vppinfra/error.h>
+#include <vppinfra/elog.h>
 #include <svm/queue.h>
 #include <vlib/vlib.h>
 #include <vlib/unix/unix.h>
@@ -764,7 +765,27 @@
    */
   if (PREDICT_FALSE
       (am->vl_clients /* vpp side */  && (q->cursize == q->maxsize)))
-    clib_warning ("WARNING: client input queue at %llx is stuffed...", q);
+    {
+      if (PREDICT_FALSE (am->elog_trace_api_messages))
+	{
+          /* *INDENT-OFF* */
+          ELOG_TYPE_DECLARE (e) =
+            {
+              .format = "api-client-queue-stuffed: %x%x",
+              .format_args = "i4i4",
+            };
+          /* *INDENT-ON* */
+	  struct
+	  {
+	    u32 hi, low;
+	  } *ed;
+	  ed = ELOG_DATA (am->elog_main, e);
+	  ed->hi = (uword) q >> 32;
+	  ed->low = (uword) q & 0xFFFFFFFF;
+	  clib_warning ("WARNING: client input queue at %llx is stuffed...",
+			q);
+	}
+    }
   (void) svm_queue_add (q, elem, 0 /* nowait */ );
 }