Add XlapTimeStampValue method.

xlap.h

@@ -103,6 +103,27 @@ typedef struct XlapTimestampTableRow {
 	typedef char XlapTimestampPlaceholder;
 #endif
 
+/*
+ * update the clock value of a timestamp by setting an explicit value
+ *
+ * This macro will cause a SIGSEGV if the application does not install a
+ * timestamp table to the socket.
+ */
+
+#ifdef XLAP
+#	define XlapTimeStampValue(sck, kind, seqno, id, value) do { \
+			atomic_load_explicit(&(sck)->tstable[kind], memory_order_acquire)->rows[(seqno) % TS_ROWS].time[ts_##id].actual.t = value; \
+		} while (0)
+#else /* XLAP */
+#	define XlapTimeStampValue(sck, kind, seqno, id, value) do { \
+			(void) (sck); \
+			(void) (kind); \
+			(void) (seqno); \
+			(void) (ts_##id); \
+			(void) (value); \
+		} while (0)
+#endif
+
 /*
  * update the clock value of a timestamp
  *