patch 8.2.5139: TIME_WITH_SYS_TIME is no longer supported by autoconf

Problem:    TIME_WITH_SYS_TIME is no longer supported by autoconf.
Solution:   Always include time.h.
diff --git a/src/os_unix.h b/src/os_unix.h
index c3a7fec..00ae239 100644
--- a/src/os_unix.h
+++ b/src/os_unix.h
@@ -128,10 +128,7 @@
 # endif
 #endif
 
-// on some systems time.h should not be included together with sys/time.h
-#if !defined(HAVE_SYS_TIME_H) || defined(TIME_WITH_SYS_TIME)
-# include <time.h>
-#endif
+#include <time.h>
 #ifdef HAVE_SYS_TIME_H
 # include <sys/time.h>
 #endif