[File] [PATCH] Fix implicit function declarations in configure with Clang 15

[Sam James]

configure gives the following warnings with Clang 15
(which makes implicit function declaraitons errors
by default):
```
-warning: implicit declaration of function 'atoi' is invalid in C99 [-Wimplicit-function-declaration]
+error: call to undeclared function 'atoi'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
 atoi(daylight);
```

Include <stdlib.h> to avoid the error.
---
 acinclude.m4 | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/acinclude.m4 b/acinclude.m4
index 77b63ff5..edcafed3 100644
--- a/acinclude.m4
+++ b/acinclude.m4
@@ -38,7 +38,8 @@ fi
 AC_CHECK_DECLS([daylight], , , [#include <time.h>])
 AC_CACHE_CHECK(for daylight, ac_cv_var_daylight,
 [AC_LINK_IFELSE(
-[AC_LANG_PROGRAM([#include <time.h>],
+[AC_LANG_PROGRAM([#include <time.h>
+#include <stdlib.h>],
 [#if !HAVE_DECL_DAYLIGHT
 extern int daylight;
 #endif
-- 
2.37.3