bpo-38068: Clean up gettimeofday configure logic. (GH-15775)

Assume gettimeofday exists and takes two arguments.
diff --git a/Python/thread_pthread.h b/Python/thread_pthread.h
index 5678b05..b9a3405 100644
--- a/Python/thread_pthread.h
+++ b/Python/thread_pthread.h
@@ -97,17 +97,10 @@
 #endif
 
 
-/* We assume all modern POSIX systems have gettimeofday() */
-#ifdef GETTIMEOFDAY_NO_TZ
-#define GETTIMEOFDAY(ptv) gettimeofday(ptv)
-#else
-#define GETTIMEOFDAY(ptv) gettimeofday(ptv, (struct timezone *)NULL)
-#endif
-
 #define MICROSECONDS_TO_TIMESPEC(microseconds, ts) \
 do { \
     struct timeval tv; \
-    GETTIMEOFDAY(&tv); \
+    gettimeofday(&tv, NULL); \
     tv.tv_usec += microseconds % 1000000; \
     tv.tv_sec += microseconds / 1000000; \
     tv.tv_sec += tv.tv_usec / 1000000; \