Add option for microsecond precision in debug.log

src/utiltime.h

@@ -12,6 +12,7 @@
 int64_t GetTime();
 int64_t GetTimeMillis();
 int64_t GetTimeMicros();
+int64_t GetLogTimeMicros();
 void SetMockTime(int64_t nMockTimeIn);
 void MilliSleep(int64_t n);