patch 8.1.1567: localtime_r() does not respond to $TZ changes

Problem:    Localtime_r() does not respond to $TZ changes.
Solution:   If $TZ changes then call tzset(). (Tom Ryder)
diff --git a/src/configure.ac b/src/configure.ac
index dbf4f42..f7a71d0 100644
--- a/src/configure.ac
+++ b/src/configure.ac
@@ -3742,7 +3742,7 @@
 	memset mkdtemp nanosleep opendir putenv qsort readlink select setenv \
 	getpgid setpgid setsid sigaltstack sigstack sigset sigsetjmp sigaction \
 	sigprocmask sigvec strcasecmp strerror strftime stricmp strncasecmp \
-	strnicmp strpbrk strtol tgetent towlower towupper iswupper \
+	strnicmp strpbrk strtol tgetent towlower towupper iswupper tzset \
 	usleep utime utimes mblen ftruncate unsetenv posix_openpt)
 AC_FUNC_SELECT_ARGTYPES
 AC_FUNC_FSEEKO