[PATCH] configure: Fix __builtin_mul_overflow() compiler support check

`UINT64_C(UINT64_MAX)' is redundant and leads to a compilation error since UINT64_C involves token concatenation, causing the check to fail.

This change fixes that by using UINT64_MAX directly, and including the appropriate header.

---

diff --git a/configure.ac b/configure.ac
index e7f59f8e6d..7b6446a1ab 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1247,8 +1247,10 @@ AC_LINK_IFELSE(
 AC_MSG_CHECKING([compiler support for __builtin_mul_overflow()])
 AC_LINK_IFELSE(
   [AC_LANG_PROGRAM(
-     [[#include <limits.h>]],
-     [[return (__builtin_mul_overflow(UINT64_C(UINT64_MAX), UINT64_C(UINT64_MAX), &(uint64_t){ 0 }));]]
+     [[#include <limits.h>
+       #include <stdint.h>
+     ]],
+     [[return (__builtin_mul_overflow(UINT64_MAX, UINT64_MAX, &(uint64_t){ 0 }));]]
    )],
   [AC_MSG_RESULT([yes])
    AC_DEFINE([HAVE_BUILTIN_MUL_OVERFLOW], [1], [define if the compiler supports __builtin_mul_overflow().])

I'm filing this as an issue because I do not have the permissions to file a merge request. I'm also attaching a copy of the above inline patch as a separate file: bind9-fix-configure-check-builtin_mul_overflow.patch