Update Musl Libc code

We now have implement all of Musl's localization code, the same way that
Musl implements localization. You may need setlocale(LC_ALL, "C.UTF-8"),
just in case anything stops working as expected.

third_party/musl/asctime.c

@@ -0,0 +1,10 @@
+/*-*- mode:c;indent-tabs-mode:t;c-basic-offset:8;tab-width:8;coding:utf-8   -*-│
+│ vi: set noet ft=c ts=8 sw=8 fenc=utf-8                                   :vi │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/time.h"
+
+char *asctime(const struct tm *tm)
+{
+	static char buf[26];
+	return asctime_r(tm, buf);
+}