pipeline: only maintain breadcrumb for debug builds

This ensures we only add a static_breadcrumb pointer to every
CoglPipeline when build with debugging enabled. Since applications may
allocate a lot of pipelines we want to keep the basic size of pipelines
(ignoring optional sparse state) down to a minimum.

Reviewed-by: Neil Roberts <neil@linux.intel.com>

(cherry picked from commit 4716312e14bc253cd174a22b3db9d2c9cf031fa1)

cogl/cogl-pipeline-debug.c

@@ -158,7 +158,12 @@ dump_pipeline_cb (CoglNode *node, void *user_data)
                           pipeline,
                           COGL_OBJECT (pipeline)->ref_count,
                           pipeline->has_static_breadcrumb ?
-                          pipeline->static_breadcrumb : "NULL");
+#ifdef COGL_DEBUG_ENABLED
+                          pipeline->static_breadcrumb : "NULL"
+#else
+                          "NULL"
+#endif
+                          );
 
   changes_label = g_string_new ("");
   g_string_append_printf (changes_label,