use idiomatic weak alias approach for defining asctime_r

get rid of a gratuitous translation unit and call frame between
asctime_r and the actual implementation of the function. this is the
way gmtime_r and localtime_r are already done.

src/time/__asctime.c

@@ -1,28 +0,0 @@
-#include <time.h>
-#include <stdio.h>
-#include <langinfo.h>
-#include "locale_impl.h"
-#include "atomic.h"
-
-const char *__nl_langinfo_l(nl_item, locale_t);
-
-char *__asctime(const struct tm *restrict tm, char *restrict buf)
-{
-	if (snprintf(buf, 26, "%.3s %.3s%3d %.2d:%.2d:%.2d %d\n",
-		__nl_langinfo_l(ABDAY_1+tm->tm_wday, C_LOCALE),
-		__nl_langinfo_l(ABMON_1+tm->tm_mon, C_LOCALE),
-		tm->tm_mday, tm->tm_hour,
-		tm->tm_min, tm->tm_sec,
-		1900 + tm->tm_year) >= 26)
-	{
-		/* ISO C requires us to use the above format string,
-		 * even if it will not fit in the buffer. Thus asctime_r
-		 * is _supposed_ to crash if the fields in tm are too large.
-		 * We follow this behavior and crash "gracefully" to warn
-		 * application developers that they may not be so lucky
-		 * on other implementations (e.g. stack smashing..).
-		 */
-		a_crash();
-	}
-	return buf;
-}

src/time/asctime.c

@@ -1,9 +1,9 @@
 #include <time.h>
 
-char *__asctime(const struct tm *, char *);
+char *__asctime_r(const struct tm *, char *);
 
 char *asctime(const struct tm *tm)
 {
 	static char buf[26];
-	return __asctime(tm, buf);
+	return __asctime_r(tm, buf);
 }

src/time/asctime_r.c

@@ -1,8 +1,31 @@
 #include <time.h>
+#include <stdio.h>
+#include <langinfo.h>
+#include "locale_impl.h"
+#include "atomic.h"
+#include "libc.h"
 
-char *__asctime(const struct tm *restrict, char *restrict);
+const char *__nl_langinfo_l(nl_item, locale_t);
 
-char *asctime_r(const struct tm *restrict tm, char *restrict buf)
+char *__asctime_r(const struct tm *restrict tm, char *restrict buf)
 {
-	return __asctime(tm, buf);
+	if (snprintf(buf, 26, "%.3s %.3s%3d %.2d:%.2d:%.2d %d\n",
+		__nl_langinfo_l(ABDAY_1+tm->tm_wday, C_LOCALE),
+		__nl_langinfo_l(ABMON_1+tm->tm_mon, C_LOCALE),
+		tm->tm_mday, tm->tm_hour,
+		tm->tm_min, tm->tm_sec,
+		1900 + tm->tm_year) >= 26)
+	{
+		/* ISO C requires us to use the above format string,
+		 * even if it will not fit in the buffer. Thus asctime_r
+		 * is _supposed_ to crash if the fields in tm are too large.
+		 * We follow this behavior and crash "gracefully" to warn
+		 * application developers that they may not be so lucky
+		 * on other implementations (e.g. stack smashing..).
+		 */
+		a_crash();
+	}
+	return buf;
 }
+
+weak_alias(__asctime_r, asctime_r);