bpo-27961: Replace PY_LLONG_MAX, PY_LLONG_MIN and PY_ULLONG_MAX with standard macros (GH-15385)

Use standard constants LLONG_MIN, LLONG_MAX and ULLONG_MAX.
diff --git a/Include/pythread.h b/Include/pythread.h
index f22e8c4..569d696 100644
--- a/Include/pythread.h
+++ b/Include/pythread.h
@@ -51,16 +51,16 @@
 #if defined(_POSIX_THREADS)
    /* PyThread_acquire_lock_timed() uses _PyTime_FromNanoseconds(us * 1000),
       convert microseconds to nanoseconds. */
-#  define PY_TIMEOUT_MAX (PY_LLONG_MAX / 1000)
+#  define PY_TIMEOUT_MAX (LLONG_MAX / 1000)
 #elif defined (NT_THREADS)
    /* In the NT API, the timeout is a DWORD and is expressed in milliseconds */
-#  if 0xFFFFFFFFLL * 1000 < PY_LLONG_MAX
+#  if 0xFFFFFFFFLL * 1000 < LLONG_MAX
 #    define PY_TIMEOUT_MAX (0xFFFFFFFFLL * 1000)
 #  else
-#    define PY_TIMEOUT_MAX PY_LLONG_MAX
+#    define PY_TIMEOUT_MAX LLONG_MAX
 #  endif
 #else
-#  define PY_TIMEOUT_MAX PY_LLONG_MAX
+#  define PY_TIMEOUT_MAX LLONG_MAX
 #endif